What surprises me most is that Norton is actually doing fairly well for once. It actually beast Kaspersky on detection, albeit not on usability. And, of course, Kaspersky is still pretty strong.
I like the free versions of Avast anti-virus and Malwarebytes’ anti-malware. Avast does automatic definition updates, and I usually see that an update has been done at least every other day or so.
I just recently switched from AVG to MSE. I found MSE was catching things AVG missed.
I would also recommend Spybot and Malwarebytes’ Anti-Malware. You can have those two as well as MSE on your computer at the same time.
If you don’t want MSE than I would go with AVG or Avast.
With AVG or Avast, I found them to slow my computer down to a crawl if I enabled the link checker. And this makes sense, since it is actually checking each link before you can go to the Internet page.
Link checkers in general are overkill for most people. If your computer can handle it, sure, why not. But if you can’t, your still 95% as safe with it off–especially if you use an adblocker or Flash blocker and leave Java off by default.