The higher the number in accel, the faster you will be able to ramp up velocity. But if you try to do it faster than your machine can stand it will skip steps and possibly stall. In other words, the faster it will go from stopped to wide open. But, this is all a balanceing act. I want my accles and vel to be as high as the machine can stand (takeing into consideration tool load + 100% safety factor) but what that will be for you is anyones guess. You will just have to play and see. I do think you will like the 10,000 steps per better though. Have a look in the members doc board. There is some information to help you with your backlash.
Brett