At an enterprise level, the leaders are all pretty much the same (Sophos, Macafee, Symantec, Kaspersky) - they are all quite good

(actually I don't like the Kaspersky UI, but that's just me:-)

At a home user level, most are actually quite poor. They do the job but are CPU and RAM hogs, so I do advise folks to go with Microsoft Security Essentials these days.