Comparing bits to Q's is like apples and oranges...
...dirtpiles and doughnuts...
The Q is MUCH more expensive, MUCH faster, fully proportional, and virtually un-moddable. Bit's are cheap, slow right out of the box, and the mod's are only limited by your own mind.
The Q steers like a tank, the bit steer with the front wheels like a real car.
The Q (as above) is fully Proportional, the Bit is either on or off. Full throttle or no go.
From what I have heard, the Q is more difficult to drive "well", but well worth the time it takes to get good at it. The Bit is a very fun car to have and modify, a must have. If you can afford a Q however, get it!
If you're checking into paying $50 for a Q, check into the Epoch Indoor Racer. It is a bit bigger, but the most satisfying car I have ever owned. It is 4" long, and goes 7 mph out of the box. If you add 1 cell, it brings it up to 10 mph. The Epoch is FULLY PROPORTIONAL and is Super Smooth. You can buy them from Tiny for around $90.