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.