Lots actually prefer to drift with out the wheel. I find it much more enjoyable though when I do drift with my DFP than with the controller, but thats me.
For racing and high speed racing drifts, the wheel is great. Teaches you alot about minimal steering as well, so you get good with throttle and brake management to steer a car, rather than just going from steering lock to steering lock...
I would say get a wheel, though wait till you can find a good deal. I do recommend the DFP, as the 900 degree steering is nice. But its not needed, so you can wait till some crazy good deal happens, or one ends up in a pawn shop maybe.