Well, I cant say I remember ever having a BSOD screen on XP, but, on Vista, I did have a genuine BSOD screen, but it wasn't Vistas fault (unless I suppressed the memory that much...)
Anyways, what I recall doing was shutting down my computer improperly (I think it was a game that I was playing that I got frustrated with while it was exiting)
I had a STOP error while booting, but, Vista has this wonderful self repair tool, and that fixed the problem without hardly any user interaction, it worked well.
As for stability of Windows 98:
It was fine when I used it, I did see quite a few errors, but it was usually the result of a scratched CD.
Quite frankly, Windows 3.11 is the most stable OS on earth... if it freezes, you press ALT+CTRL+DEL, a blue screen pops up, tell you whats wrong, and says "Press ENTER to close the program, Press ESC to see if the program starts to respond again, or press ALT+CTRL+DEL again to restart your computer"
Press ENTER, and all is well again.