I would actually go with Avira Personal Antivirus, though Im using Avira Premium Security Suite now,
I'd say Avira's the best that I've tried so far, it's actually got the quickest scanner out of all the scanners I've tried, it has a few more false positives than Avast, but it also catches more possible trojans/viruses which makes it safer for your computer
I mainly like Avira Antivirus overall for its speed
Though, about Avira Premium or Premium Security Suite though, I recomment disabling MailGuard and WebGuard from time to time, e-mails usually filter themselves into spam mail already, and the WebGuard checks every page you're going through, and that slows down your web surfing speed
Unless, you're Unsure of the site(s) you're going on, I recommend just leaving WebGuard off to increase web surfing speed
And about Avira Premium Security Suite, on top of what Avira Antivirus & Premium have, Avira Antivirus Premium Security Suite has a firewall and it's very effective, I've never had any problems with it
Other Antiviruses:
I've used alot of software before, Nod32 was said to have a fast antivirus scanner (well, it took 3-4 hours on my labtop,then again my labtop's kinda slow compared to my computer)
After using Avast Professional, I've noticed that it was rather effective, but, as it keeps checking every web page you use, it slows down your computer performance(speed), so I switched from avast to other things when I noticed that
I know how Norton works, cuz my dad installed Norton on the computer from the beginning, it's really great security and really hard to crack in terms of it's complex-firewall, but it uses alot of computer resources which makes your computer work alot slower, which makes Norton cause your computer to run quite a bit slower than it could
And McAfee, my dad installed on the labtop, in my opinion, it's sort of like Norton, because it doesn't give you many options other than seeing, quarantining/deleting viruses, but, then again -
Norton and McAfee both are similar in that they use alot of resources
Avast Professional was said to be light, it has 8 scanners(6 scanners in the free-home version)and another thing to know about avast is that it comes with a light firewall, so if you install a firewall with avast, you're gonna want to disable 1 scanner, the "Web Shield" scanner, that's the light firewall that comes with Avast
And Nod32 was rated really high, and compared interestingly close to Kaspersky Antivirus, which I Also Tried, Kaspersky Internet Security actually.
Kaspersky Internet Security has a great looking interface but all of its scanners are rather slow in my opinion