I just got Computer Which over the weekend and they do a review of computer security software.
Their top paid-for choice was Bitdefender Internet Security which scored 80%.
Others paid-for scoring high were F-Secure (78%), Norton (75%), Trend (75%), Avast (73%), Avira (73%), Panda (72%).
Note BitDefender FREE scored 75% (against the paid for 80%)
WebRoot was not tested, not sure why.
Note that while many people push the "free" anti virus products they are often basic versions of the products and don't include premium features like phishing protection, safe banking etc.
They are given away free as a sort of "loss leader" hoping that if you use the free product you may then move to the paid for product.
Also note that the "best" security products are changing all the time.
New PC security problems are being found all the time and it depends how quick a company "find" these problems and fix them.
So a particular product may be top dog at the moment, but well down the list in 6 months time.
For example when Which did their last PC security review they put Sophos as their top free anti virus product. It is now bottom of the ones they tested with a score of only 58%.