The most important things to look for in selecting a wheel are:
Size of the wheel head.
At least 14" is usually desired,
but not required for small pots.
Size of the motor.
This determines the maximum amount of clay
you can center. Professionals look for wheels that can center at
least 50 lbs of clay. It usually takes years of practice before
you can center this much clay.
Reversing switch.
If you are left handed, this allows the wheel
to spin the opposite direction.
Drilled holes for bats.
This allow you to use bat pins to
attach bats, so you can easily remove them and start throwing on another
one.
Work space.
Some wheels give you work area to put your tools,
water bucket, etc. Unless you are going to build your own platform
some type of work surface is required.
Splash pans.
Some are included, some are sold separately.
The highest price does not necessarily mean the best wheel.
Look for a balance of features that are in your price range, and you can
expect all these wheels to last a long time!