Do i need both SpywareGuard and Spybot as resident?

SpywareGuard and Spybots resident "Teatimer" resident systems protection, appears to provide the same type of protections. Spybot however, seems to watch out for incidents than SpywareGuard(which can be annoying). I want decent protection, but i also want to keep the resource use lower.

Is it enough to use SpywareBlaster+Spybot(using resident protection) or Blaster+Guard or does it make sense to also have both resident programs running? ( i always install ad-aware free for manual scanning).

As a related question, does Spybots resident program use more or less resources than SpywareGuard?