Read some of the differences between DC17 Animal and DC33 Multi Floor below.
In this post, DC17 refers to DC17 Animal, DC33 refers to DC33 Multi Floor.
Dyson DC17 vs DC33
images from manufacturer

Brushbar Control Type
The brush control button of DC17 is located next to the ON/OFF switch, so you do not have to bend down to control; whereas the brushbar control of DC33 is on the cleaner head thus you have to bend down to turn it on/off.

Suction Power
DC17 has a suction power of 220 air watts while DC33 has 240 air watts.

Tools
DC17 comes with a mini turbine head, carpet care kit, and low reach floor tool, whereas DC33 comes with combination accessory tool and stair tool.

Price
DC17 Animal is priced at $549.99 while DC33 is priced at $399.99 at Dyson.com. (prices checked on August 7, 2011)

Bin Capacity
DC17 has a bin capacity of 0.625 gallons while DC33 has a 0.61 gallon bin.

Weight
DC33 is lighter than DC17.
DC17 weighs 20.79 pounds while DC33 weighs 17.6 pounds.