Slower or not, lets just see OS4 and MOS running on 933MHz G4 systems and sit them side by side with XP or 2003 on the fastest x86 you can find...
And then someone comes along and throws BeOS into the mix and all of a sudden the x86 looks utterly renewed.. Windows is utterly pathetic as far as platforms go, slow, bloated and everything else. You put a lightwieght OS onto x86 hardware and watch it fly. Hell, even linux can utterly outperform Win2k3 on the same system doing the same sorts of jobs (UT in morphix is in order of magnitude faster than on Win2k).
Obviously for processor intensive work there's no contest but I've seen my OS3.5 on my 040 be more responsive than my friends AlthonXP 2800 many occasions
As have I, I have not however been able to say the same regarding BSD, linux or BeOS.
