I have used them all. Avast is bloat, Avira turned into crap and is a living bitch to uninstall. McCarefree and Norton are trash. Really, they are. If you want a definition-based anti-virus (which they all are) then I suggest Bitdefender Free. It's lightweight and cloud-based so that it can help mitigate polymorphic malware, i.e ransomware. But definition-based anti-virus solutions are NOT full proof and polymorphic malware can slip though. So if you use an anti-virus, I would check out Sandboxie for your browser. It's free for the browser only. The only caveat is that with the free version after 30 days when you launch your browser with Sandboxie it will have you wait 5 seconds. Small price to pay for free. If you wanted to buy it it's an annual fee and hell if I'm paying that. If it was a one time fee I'd buy it.
What Sandboxie does is isolate everything in the browser so nothing touches your computer unless you allow it with recovery.
Going beyond a typical definition-based anti-virus you might be interested in a catch all approach. There are two solutions. 1) Faronics Anti-executable and 2) A whole virtualization approach of the operating system using something like Shadow Defender.
Faronics Anti-executable will alert you to anything that wants to execute on your computer. I have tossed a bunch of malware at it up to and including ransomware and they never got past.
Shadow Defender is probably even more powerful. If you get hit with a virus all you have to do is restart the computer and all is back to the way it was. This is because nothing sticks in the virtualized environment. The only caveat to this is that you have to setup file and/or folder exclusions in the program so that files saved to those locations stick on reboot. Folders to be excluded in Shadow Defender's options might be your My Documents folder, videos folder, pictures folder, music folder, downloads folder the trash can and the browser profile so that bookmarks and add-ons stick. The recycle bin path can be found under C drive. You have to go to folder options in your computer and show protected OS items, then you can browse to the $recyclebin path under C drive to exclude it in Shadow Defender. If you need to install or update a program you can either add both program files folder to the exclude list or reboot the PC twice after you turn off Shadow Defender. Once you update or install a program you can turn Shadow Defender back on. Note that registry items are protected as well. Nothing sticks there either unless you setup exclusions, but that's a pain since there could be any number of registry entries. If all this sound like a major pain in the ass, then Faronics Anti-executable might be your best bet.
Like I said. I have tossed boat loads of malware at anti-executable and I did the same thing to Shadow Defender. Nothing got past.
Bitdefender Free is great and I have it on my parent's computer and my aunt's computer. The only issue with it is it protects so-called Windows debugging and it WILL mess around with game hacks and or other game-like programs. Like I play Generals Zero Hour (yes, an old game) but if I use the Gentool it won't run because Bitdefender Free protects debugging and I guess Gentool needs debugging to work. Debugging is bad business in terms of malware protection, so that's why Bitdefender Free does that.
To summarize. Check out Bitdefender Free and/or Sandboxie. Take it up a notch and check out Faronics Anti-executable or Shadow Defender.
Any questions ask. It would be wise to get into the habit to scan all downloads at the Virus Total website. And also clone your computer every so often to an external USB HDD.