Also it seems that the framerate is slower when eg. game is played in 640x480 when WB is set to 1024x768 THAN to first change WB-screenmode to be the same as the game will have.
quick Quake 2 test (timedemo 1, demomap demo1.dm2):
WB 1024x768 - game 640x480 (window, without FullWin) - 19.6fps
WB 640x480 - game 640x480 (window, with FullWin) - 21.0fps
strange...but positive
PS. if you wonder the faster 21.5fps I posted before that's because I changed glmaxparticles from 128 to 256 (looks nicer)...