I can only say ZA atm mostly out of habit and that it has a great anti-stuff engine. (I`d like to have the viral/spy stuff on it`s own minus the firewall >.<)
However, I will also add it`s not very online game friendly. Sure u can get it to co-operate, but even when it does u lose out a tad. (usually I turn it off)
Now, I am advised that NOD32 isvery friendly to gaming, but I haven`t tried it yet.
The other thingies I`ve had bad experiences with, but I will say that when I have chosen to use them I had an inclin that there were problems before-hand.
Shameful that u`d need to use such things as registry mechanic to do windows own house keeping.