Some mice are indeed awful, but there's little to choose from between both decent mice. In particular, I never bought into the whole "wireless is too slow" thing - I have both plugged in as we speak, just got off Q3A and didn't notice a difference. If anything, the drag of the cord makes the wired slower!
What IS important is a decent gaming surface. I have a wooden table, and the slight difference in colour in the wood grain sometimes makes the optical sensor skip a bit in its tracking. I use a mousepad, but it's a cloth one and the mouse feet don't slide on it as smoothly as they could. Saw some decent mousepads about but they cost £10-15 which I thought was ridiculous for a rectangular piece of monochrome plastic!