I honestly despise Norton 360 more than McAfee, both suck up completely unreasonable amounts of PC resources and they are both expensive. I've used a lot of scanners on the market and by far the best free virus scanner I've used was AVG, it's simple, small, and to the point. It's easy to use and has never failed me. The best 'subscription' antivirus I've used has by far been kaspersky, but then again i got it free from a promotion at best buy.
--but honestly, the best antivirus is you. You decide what you download and what websites you visit *cough* so use common sense.