Norton represents the gold standard in Anti-Virus programs in terms of name recognition and company reputation. They've been around forever, and were the first big virus program. Norton looks to make things simple, with constant real-time virus / malware / spyware protection, frequent updates (several times a day sometimes), and a set it and forget it dashboard. There's a lot to like here.
Norton has good performance, but might still be a little beefy for older machines. It's also the priciest of the bunch, which might be an issue for some consumers.
The best. It's the #1 name in virus protection, and they back this up by being a "constantly updating" program. I've seen it update several times a day when new attacks come out. You can feel good with Norton protecting your system.
A lot of people consider Norton the best. While it's a little more expensive, Norton is the top name in the industry, and a good all-around value for virus protection.