I'll let someone else do the beta testing with Anvi Smart Defender. However, I'm not knocking the software, it may be good. It would need to develop a good reputation for many to consider it.
Avast just upgraded their free AV to version 7, and you get a 20 day trial of Avast Internet Security with it, if you want. It even runs on Windows 8 CP, I'm using their IS now. Mainly for the SafeZone browser.
Avast & MSE are the 2 best choices for a free AV for Windows 7. One great feature of Avast Free, is their BootTime scanner, you schedule it, reboot, and after the Windows symbol appears, it begins to scan your entire system. Even your entire hard drive, unless the user excludes partitions. It's highly adjustable, but don't jack every setting to the max. In doing so, your computer will be slowed.
A great feature of MSE is that for the most part, it does the work for the user. There's no graphs showing what it's scanning (your file system), but it's actively scanning as long as the computer is on. There are a few adjustments, but the default works for most users. One adjustment that the user needs to make is the time which the daily short scan runs. And if your computer is a low spec one, you may wish to lower the CPU usage (default is 50%). MS Update also keeps MSE updated, but if you wish to do a scan, you can manually check for updates first.
With nothing to lose, try both & see which is best for you. Whichever you get, also have the free version of Malwarebytes installed, as it can find some nasty things that can bypass any AV/IS software, paid or free. A weekly full scan doesn't take long, and is worth doing.
AVG, no. Just NO. Don't do it with Windows 7. There are tens of thousands of forum posts in regard to Windows 7 having BSOD's with AVG installed. Don't be a statistic to add to the list. Plus, it's one of the hardest ones to remove from your computer, especially their IS suite.
Cat