The difference between Hoover SH20030 and S2220 are:
Hoover S2220 vs SH20030
images from manufacturer

Price:
The Hoover SH20030 is a bit more expensive, it is priced at $64.99 whereas the S2220 is priced at $59.99 at hoover.com (prices checked on July 13, 2013)

Edge Cleaning:
The SH20030 features Brushed Edge Cleaning that removes dirt and dust up against edges whereas the S2220 does not.

Height Adjustment:
The S2220 has 3 manual height settings whereas the SH20030 features automatic adjustment.

Filtration:
The SH20030 uses Micro filtration while the S2220 use standard filtration.

Hoover WindTunnel Technology:
The SH20030 features Hoover WindTunnel Technology while the S2220 does not.

Warranty:
The SH20030 is backed up with a 2 year limited warranty while the S2220 carries 1 year limited warranty.

Nozzle Width:
The SH20030 has a nozzle width of 11 inches while the nozzle width on S2220 is 9-inch.

Color:
The SH20030 is grey while the S2220 is red.

Similarities:
They are bagless.
They both have spinning brush and brush on/off switch.
They have 20 ft cable.
120 volts motor.

Read manuals for more details:
SH20030 manual: http://hoover.com/file/642/
S2220 manual: http://hoover.com/file/617/

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The difference between Hoover S2220 and S2200 are:
Hoover S2200 vs S2220
images from manufacturer

They are in different colors.

The S2220 has a motorized brushroll that can be turned off whereas the S2200 does not have a beater bar.

On hoover.com product pages, it states that the S2220 has a 8.2 amp motor while the S2200 has a 6.8 amp motor.

The S2220 is a little more expensive than the S2200, it is priced at $59.99 whereas the S2200 is priced at $49.99 at hoover.com (prices checked on July 12, 2013)

Otherwise, they are identical.

They are bagless, have no bag to change.

They have 20 ft power cord.

They feature slot for hanging up.

They carry one year limited warranty.

120 Volts.

3 level height adjustments.

9-inch Nozzle Width.

They have no attachments, no headlight, no speed settings.

Learn more by downloading manuals:
Hoover S2220 manual: http://hoover.com/file/617/
S2200 manual download: http://hoover.com/file/618/

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The difference between Hoover UH30300 and UH30310 are:
Hoover UH30310 vs UH30300
images from manufacturer

Standard VS Pet:
The Hoover UH30300 is a standard model while the UH30310 is pet model.
Pet model features Activated Carbon to absorb pet odors and other household odors whereas the standard model does not have.
Pet models have tools that are designed for pets, the air driven pet hand tool and the pet upholstery tool feature rubber wipers to help remove pet hair from furniture and upholstery. While the tools on standard models do not feature rubber wipers.

Hose: The UH30310 has a longer stretch hose.
The UH30300 comes with a 8 ft stretch hose whereas the UH30310 has a 12 ft deluxe stretch hose.

Price: The UH30310 is $10 more expensive than the UH30300.
The UH30310 is priced at $149.99 at hoover.com whereas the UH30300 is priced at $139.99 (prices checked on July 7, 2013)

Other than that they are almost the same.

They are T-Series Windtunnel bagged upright vacuum cleaners.
They feature Brushroll Shutoff that allows you to use it on bare floors without the risk of damaging the floor by the spinning brush.
Equip with Headlight to illuminate dark areas for thorough cleaning.
Full Bag Indicator to tell you when to check bag and filter.
5 Level Height Adjustment that allows you to adjust to clean different flooring types.
Feature D-Shaped Handle.
Weighs about 15 pounds.
Equip with 12 amp motor.
Have a 30-ft cord.
13.5 nozzle width.
HEPA media filters traps more than 99.9% of tiny particles down to 0.3 microns.
No cord rewind.

You can learn more by downloading the manuals:

UH30300 manual
http://hoover.com/file/543/

UH30310 manual
http://hoover.com/file/544/

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Below are the difference between Hoover UH30010com and U5140-900
Hoover U5140900 vs UH30010COM
images from manufacturer

Portable Canister Vacuum:
The UH30010COM comes with a portable canister vacuum cleaner for portable cleaning while the U5140900 does not have such a canister.

Height Adjustment:
The U5140900 has 5 manual height settings while the UH30010COM adjusts height automatically but no manual settings.

Brush Speed:
The UH30010COM has 2 speeds while the U5140900 has only 1.

Full Bag Indicator:
The UH30010COM features full bag indicator while the U5140900 does not.

Headlight:
The UH30010COM features headlight whereas the U5140900 has no headlight.

Bag Type:
The U5140900 use Allergen Media bag that can capture 99% of particles down to 5 microns.
While the U5140900 features HEPA media bag that can capture 99.97% of particles down to 0.3 microns, it gives you better air quality than allergen media bags.

Location of ON/OFF Switch:
The ON/OFF Switch on UH30010COM is on the top of the Handle whereas the one on U5140900 is located on the top left of the vacuum body.

Tools:
The UH30010COM comes with one Telescopic Extension Wand, one Crevice Tool, one Dusting Brush, one Floor brush.
Whereas the U5140900 has 2 Extension Wands, one Crevice Tool, one Dusting Brush, one Upholstery Tool.

Nozzle Width:
Nozzle Width of the UH30010COM is 14 inches while it is 15-inch on the U5140900.

Cord Length: The UH30010COM has a much longer cord.
The cord length on the UH30010COM is 35 ft while it is 25 ft on the U5140900.

Handle:
The UH30010COM features D-Shaped Handle whereas the U5140900 features Standard Grip Handle.

Weight: The UH30010COM is lighter.
The UH30010COM upright unit weighs less than 12 pounds while the U5140900 weighs more than 16 pounds.

Warranty:
The UH30010COM carries 5 year limited warranty while the U5140900 has only 1 year limited warranty.

Price: The UH30010COM is $200 more expensive than the U5140900.
UH30010COM is priced at $299.99 while the U5140900 costs $99.99 (prices checked on July 01, 2013 at hoover.com)

Color:
The UH30010COM is grey while the U5140900 is blue.

Similarities between Hoover UH30010com and U5140-900:
They are bagged upright vacuum cleaners.
equip with motorized brush but no brush On/Off switch;
12-amp motor;
no auto cord rewind.

You can also download the manuals to learn more, here are the links:
UH30010COM manual: http://hoover.com/file/537/
U5140-900 manual: http://hoover.com/file/431/

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