Just a little extra tidbit:
The only difference (in theory) between the 2 is stability.
A wireless connection may drop out from time to time. This is normally due to interference, distance from router and/or crap hardware (the free router you get from your ISP generally have sub-par antenna's in them, although I think the new BT one's are good).
Your actual speeds when connected on the other hand should be the same.
It usually comes down to location, if your ps3 is near the router you'd be better off going for wired, but if it's too far away you should be fine with wireless.
In terms of in-game connection/speed you aren't disadvantaged by playing wirelessly.