There will be some difference, you'll probably be best going for the 12x1 if you've only got the choice of these two motors.
the 10x2 will have more revs, and therefore more top speed but it sacrifices torque to get this. It will also eat your batteries quicker.
The 12x1 is still a very fast motor, and both will require regular maintanence, including skimming the comm, which will mean either buying a lathe at over $100, not sure on US prices, or finding someone local to do it for you for a small fee eveery time. If you're just street bashing then you're better off with a slower motor, like a 17x2 or even a stock motor. They require less maintanence, although they still require some, and will run for longer on one set of cells.