Originally Posted by Leviathan
I don't think you can nominate a definite winner there.
Don't know much anything about OS/2 or BSD, but the Windows Scheduler is geared more towards short response time than the Linux Scheduler (shorter timeslices) which also means there are more task-switches => more time wasted switching tasks.
Also, Windows has a mechanism to give UI-Threads higher priority so user interaction is again more responsive than on Linux (and propably most other OS) at the cost of raw processing power.
Besides, Windows has had working Kernel-Preemtion since Windows NT so all drivers for WinNT/Win2k/WinXP can be properly preempted.
Linux on the other hand has introduced Kernel-Preemtion only with v2.6 and there are still some drivers that don't work properly if they are preempted so it's adviced to not use that feature. (Quote: "Say Y here if you are feeling brave and building a kernel for a desktop, embedded or real-time system. Say N if you are unsure.")
Depending on Application, each system has its advantages.
Funny thing is though, is the short response time it seems no one really wants. I remember Linus Torvalds talking about it and it just hasn't been an issue people want improved.
About the BSD KSE, here's a good read.