The major difference between UH70140 and UH70120 are:

Brushroll ON/OFF Switch:
The Hoover UH70140 equips with brushroll ON/OFF function, you can step a petal to turn on or shut off the brushroll for suction only mode, whereas the UH70120 has no brush ON/OFF switch.

Height Adjustment:
Both of them equip with the height adjustment, however, there is slight difference. The UH70120 has 5 height settings while the UH70140 has 3 levels to adjust.

Headlight:
The UH70140 has a headlight that allows you to clean areas like dark corners thoroughly whereas the UH70120 have no such headlight.

Air System:
The UH70120 features Dual Cyclonic Air System while the UH70140 uses Multi-Stage Cyclonic Technology.

Color:
The UH70120 is green while the UH70140 is red.

Price: The UH70120 is $20 cheaper than the UH70140.
The UH70120 is priced at $129.99 at hoover.com while the UH70140 is priced at $129.99 (prices checked on June 23, 2013)

Similarities between UH70140 and UH70120:
have auto cord rewind function;
equip with motorized brush;
powered by 12 amps motor;
weighs 16.5 pounds;
8 ft stretch hose;
13.5-inch cleaning path width;
include HEPA filter;
2 year limited warranty;
comes with onboard tools: Turbo Hand Tool, Upholstery/Dusting Brush, Extension Wand, Crevice Tool;
indicator to tell you when to check dust bin and filter;
scuff guard bumper protects your furniture;
fingertip power control.

You can learn more by reading manuals:
UH70120 Manual Download: http://hoover.com/file/570/
UH70140 Manual Download: http://hoover.com/file/588/

Please share below if you know more difference between Hoover UH70120 and UH70140.

Below is the difference between Hoover UH70120 and UH70210:

UH70210 vs UH70120
images from manufacturer

The Titles:
UH70210: T-Series WindTunnel Pet Rewind Bagless Upright model #UH70210
UH70120: T-Series WindTunnel Rewind Plus Bagless Upright model #UH70120
Thr UH70210 is a model for pets while the UH70120 is not a pet specific model. Some major difference between these hoover T-Series WindTunnel general model and pet model are the filter and tools they come with.

Filtration:
Pet models have a Carbon Filter to absorb pet smell, the UH70210 features this whereas the general model UH70120 has no Carbon Filter.

Onboard Tools:
The UH70120 comes with a Turbo Hand Tool, a Crevice Tool, a combo Upholstery/Dusting Brush, and a 12″ extension wand.
The UH70210 comes with a Turbo Pet Hand Tool tool, a Crevice Tool, a Pet Upholstery Tool, and a 12″ extension wand.
The difference between the general Turbo Hand Tool and Turbo Pet Hand Tool, combo Upholstery/Dusting Brush and Pet Upholstery Tool are the pet tools feature rubber blades to help grab pet hair from surfaces that are being cleaned while the standard types of tool have no rubber blades.

Handle:
The Hoover UH70210 has a folding handle which can be folded down for storage while the handle on UH70120 cannot be folded.

Brushroll ON/OFF Control:
The Hoover UH70210 features a pedal to turn on/off the brushroll whereas the UH70120 does not have a switch to turn off the spinning brush.

Headlight:
The UH70210 equips with a headlight while there is no headlamp on UH70120.

Price: The UH70210 is $30 more expensive than the UH70120.
The UH70210 is priced at $159.99 at hoover.com while the UH70120 is priced at $129.99. (prices checked on June 22, 2013)

Product Weight: The UH70210 is heavier.
The UH70120 has a weight of 16.5 pounds while the UH70210 weighs 17.8 pounds.

Color:
The UH70210 is blue whereas the UH70120 is green.

Similarities between UH70210 and UH70120:
equip with motorized brush;
have 12 amps motor;
bagless;
25 ft cord;
8 ft long hose;
13.5-inch nozzle width;
have auto cord retractor;
have HEPA filter;
2 year limited warranty;
features Dual Cyclonic Air System;
feature 5 adjustable height settings but suction power is not adjustable.

Download manuals:
UH70120 Manual: http://hoover.com/file/570/
UH70210 Manual: http://hoover.com/file/574/

Please share below if you know more difference between Hoover UH70600 and UH70210.

Here are some of the difference between Hoover UH70210 and UH70600:

UH70210 vs UH70600
images from manufacturer

Cyclonic Action Air System:
The UH70600 features Multi-Cylonic Air System whereas the UH70210 features Dual Cyclonic Air System.

Weight: The UH70210 is lighter.
The UH70600 has a weight of 18.4 pounds while the UH70210 weighs 17.8 lbs.

Price: The UH70600 is $40 more expensive than the UH70210.
The UH70600 is priced at $199.99 at hoover.com while the UH70210 is priced at $159.99. (prices checked on June 21, 2013)

Height Adjustment:
The UH70600 has 7 levels of height adjustment to fit different floor types while the UH70210 features 5 levels to choose.

Filtration:
To absorb pet odors in your house, the UH70210 features a Carbon Filter whereas the UH70600 does not includes this pet specific
filter.

Onboard Tools:
The UH70600 comes with a Crevice Tool, a combo Upholstery/Dusting Brush, and an Extension Wand.
The UH70210 comes with tools that are good for removing pet hair: a Turbo Pet Hand Tool and Pet Upholstery Tool, they feature rubber blades to grab pet hair from upholstered surface, sofa and other furniture.

Wand: The wand on UH70600 is longer.
The extension wand on UH70600 is 20-inch long while the UH70210 comes with a 12-inch wand.

Hose: The hose on UH70600 is much longer.
The UH70600 has a 15 ft hose while the hose on UH70210 is 8 ft long.

Nozzle Width: The nozzle width on UH70600 is wider.
The UH70600 features a wide nozzle of 15-inch while it is 13.5 inch on UH70210.

Handle:
The Hoover UH70210 has a handle that you can fold it down for easy storage whereas the handle on UH70600 cannot be folded down.

Cord Length: The cord on UH70600 is a longer.
The UH70600 has a 28 ft long cord while the cord on UH70210 is 25 ft long.

The Titles:
UH70210: T-Series WindTunnel Pet Rewind Bagless Upright model #UH70210
UH70600: WindTunnel Max Multi-Cyclonic Bagless Upright model #UH70600

From the titles we can see that UH70210 a Pet specific model while the UH70600 is not.

Similarities between UH70210 and UH70600:
they are bagless;
have headlight to help clean low light areas;
equip with motorized brush with On/Off switch;
12 amps motor;
feature auto cord retractor;
have HEPA filter to trap tiny particles and make air fresher;
2 year limited warranty;
no function to adjust suction.

Download manuals to learn more:
UH70210 Manual: http://hoover.com/file/574/
UH70600 Manual: http://hoover.com/file/579/

Please share below if you know more difference between Hoover UH70600 and UH70210.

Below is the difference between Hoover UH70120 and UH70600:

UH70120: T-Series WindTunnel Rewind Plus Bagless Upright
UH70600: WindTunnel Max Multi-Cyclonic Bagless Upright

UH70120 vs UH70600
images from manufacturer

Color:
The UH70600 is blue whereas the UH70120 is green.

Brush ON/OFF Control:
The Hoover UH70600 features a foot pedal to switch the brush while the UH70120 has no brush ON/OFF switch.

Height Adjustment:
The UH70120 has 5 height adjustments to fit different cleaning requirements while the UH70600 has 7 settings.

Onboard Accessories:
The UH70600 comes with an Extension Wand, a Crevice Tool and a combo Upholstery/Dusting Brush.
Whereas the UH70120 comes with an Turbo Hand Tool, an Extension Wand, a Crevice Tool and a combo Upholstery/Dusting Brush.

Wand: The wand on UH70600 is longer.
The UH70600 comes with a 20-inch Extension Wand whereas the hose on UH70120 is 12-inch long.

Hose: The UH70600 has a longer hose.
The UH70600 comes with a 15 ft hose while the UH70120 comes with a 8 ft hose.

Headlight:
The UH70600 equips with a headlight whereas the UH70120 has no headlamp.

Cord Length: The UH70600 has a bit longer power cord.
The UH70120 has a 25 ft cord while the cord length of UH70600 is 28 ft long.

Product Weight: The UH70600 is heavier.
The UH70120 has a weight of 16.5 lbs whereas the UH70600 weighs 18.4 lbs.

Nozzle Width:
The UH70120 has 13.5-inch nozzle width while the UH70600 has larger nozzle that is 15-inch wide.

Cyclonic Action:
The UH70120 features Dual Cyclonic Air System while the UH70600 features Multi Cyclonic Action.

Price: The UH70600 is $70 more expensive.
The UH70120 costs $129.99 whereas the UH70600 is priced at $199.99 at hoover.com (prices checked on June 20, 2013)

Similarities:
They are bagless.
12 amps motor.
Equip with auto cord rewind.
Feature HEPA filter to trap dust and improve air quality.
No suction adjustment.
2 year warranty.

For more details, download the manuals:
UH70120: http://hoover.com/file/570/
UH70600: http://hoover.com/file/579/

Please share below if you know more difference between Hoover UH70600 and UH70120.

The Hoover UH70400 belongs to the WindTunnel Air serials whereas the UH70210 is one of the Pet models of the T-Series WindTunnel serials.
The difference between Hoover UH70400 and UH70210 are:
UH70210 vs UH70400
images from manufacturer

Cyclonic Action Air System:
The UH70210 features Dual Cyclonic Air System while the UH70400 features a Multi-Cylonic Action.

Tools:
The UH70210 is a pet model, it comes with Air Driven Pet Hand Tool and Pet Upholstery Tool with rubber blades to help remove pet hair from furniture and upholstery, whereas the UH70400 includes a Upholstery/Dusting Brush combo tool, but does not have the air powered tool, it also comes with a 3-in-1 Combination Tool, and a Crevice Tool. The UH70210 also has a Crevice Tool.

Filtration:
The UH70210 equips with Carbon Filter to absorb pet odors whereas the UH70400 does not feature the Carbon Filter.

Motor Amps:
The UH70400 equips with 11 amps motor whereas the UH70210 has 12 amps.

Height Adjustment:
The UH70400 uses automatic height adjustment to fit the floors you vacuum whereas the UH70210 uses manual height setting, there are five options to select.

Brushroll Switch Location:
The brushroll switch of Hoover UH70400 is on the top of the vacuum body whereas the UH70210 equips with a foot pedal at the left side of its base to switch the brushroll.

Nozzle Width: The nozzle width on UH70210 is wider.
The UH70400 has a relative small nozzle, its width is just 11-inch while the UH70210 has 13.5 inch nozzle width.

Cord Rewind:
There is a cord rewind pedal on the UH70210 that you can tap to retract the cord automatically whereas the UH70400 does not feature auto cord rewind.

Cord Length: The UH70400 has a longer cable.
The cord on UH70400 is 30 ft long whereas the cord length of UH70210 is 25 ft long.

Color:
The UH70400 is grey with a little green whereas the UH70210 is blue.

Weight: The UH70400 is over 5 pounds lighter.
The UH70400 has a weight of 12.4 pounds whereas the UH70210 weighs 17.8 pounds.

Headlight:
The UH70400 has no headlamp for dark spot cleaning whereas the UH70210 features one.

Power ON/OFF Switch Location:
The ON/OFF Switch on the UH70210 is on the handle while the UH70400 has it on the top of the vacuum, next to the brushroll switch.

Deep Recline:
The Deep Recline feature allows the vacuum to recline flat to get under furniture. The UH70400 features it whereas the UH70210 does not.

Handle:
The Hoover UH70400 features an adjustable handle with built-in wand that you can remove for cleaning hard to reach places, the handle cannot be folded, whereas the UH70210 has a foldable handle that can be folded for compact storage, but it is not adjustable, and its wand 12 inch extension wand is not built-in type.

Hose:
The UH70400 includes a Quick Fit Hose and a 8 ft Stair Hose whereas UH70210 has a 8 ft long stretch hose.

Price: The UH70400 is $30 cheaper than the UH70210.
The UH70400 is priced at $129.99 at hoover.com whereas the UH70210 costs $159.99. (prices checked on June 19, 2013)

To learn details, download manuals:
UH70400 Manual: http://hoover.com/file/578/
UH70210 Manual: http://hoover.com/file/574/

Please share below if you know more difference between Hoover UH70400 and UH70210.