Whatever you use, scour its Settings/Configuration panels for optional features that you might want to enable. In the case of Kaspersky, enabling the heuristics on all the detection modules would be a good idea IMHO. In the case of AntiVir, I'd set the heuristics to maximum at the risk of more false positives, since their heuristics appear to be one of their strongest suits.
Also look for optional types of detections (spyware, adware, dialers, riskware, potentially-unwanted programs, bread mold, poisonous mushrooms, and nasty girls you shouldn't go out with) and enable them.