The differences are from the added overhead of the player -- it accesses a lot more stuff about your computer and keeps more state variables -- the performance hit is nominal - and I think Macromedia anticipated advances in hardware in time would make the performance differences moot.

I personally have seen no differences in the players using multiple resolutions - running xp-os x-win2K-win98 -- if there is a difference, it's never more than maybe 1 FPS -- the big determining factor I found was CPU and ram just like always --