Hmm, I didn't much like Avira, but that was more aesthetics. The constant nag screens were annoying. Anyway...
Avast seems to be okay. Its footprint is reasonably small, it's updated often, there's a good deal of flexibility as to configuration. I like the boot scan option. Of the free AV utilities, it's my favorite. [shrugs] No defense is perfect, as I'm sure you know. A wary user at the keyboard helps as well.
Good luck.
