I've been using Avast for quite awhile, no complaints, including since I upgraded to 10. I don't know which one is "the best" these days as it seems to flip around and I haven't looked ilately. Course, I'm not exactly downloading illicit Mexican midget hooker donkey shows or opening attachments so I can fill out the bank form and claim the life savings of my diamond mine owning Nigerian Uncle either, so I'm not generally putting it to extreme tests.
I pair it up with various more specific spyware/malware programs and have had good luck with it. Namely Malwarebytes, SuperAntiSpyware, Spybot, and Iobit Malware Fighter. Only one I leave with active protection up is the Antivirus. I just keep the others on hand to run periodically, if I think there is a problem, or if the AV hits on something I will run the others to make sure it gets everything.