A very long time ago these were on top of their game, Spybot and its Tea Timer has in the past conflicts with some startup entries (avast for one) . SAS is better but still old school, so as mentioned if you were going to keep one this would be it.
MBAM is better, but that can be a resource hog, though version 3.1 is meant to be lighter. I abandoned it when version 3.0 came out.