Tehre are about a half dozen programs that tend to perform well on various tests. Norton, Avast, Kaspersky, Bit Defender, F Secure and Avira seem to get top marks. The problem is that they flip flop in performance on various measures across the tests.
Others not so good. Microsoft Security Essentials is one of the mediocre ones, and it doesn't work well with other anti-virus software. Free Avast might do better.
Dora
Okay there are several things wrong with your post here.
First and foremost, I dont know where you got this information that Norton gets rated high. I have yet to see that happen. Everyone who knows anything about PC Security will tell you to stay away from Norton and McAfee as if your life depended on it.
Next MSE is no where near mediocre. In fact it was higher rated than Norton, Avast and Avira just recently from the Independent AV Group. The group of people who test out all AV programs and rate them but do not get kick backs from a single one. Unlike PCMagazine which biggest financial backer is Norton and they dont want to bite the hand finances them so they always rate them high.
Not to mention MSE is a stand alone product just like all the ones you mentioned above. It is not to be used in conjunction with any other software. That is why it doesnt work well with other AV software cause it is not designed to. Not a single one of them are. If you have more than 1 AV installed, I am willing to bet you that you are infected. Despite both your programs saying your clean.
The fact of the matter is that any AV runs on a definition. But if you have 2 AV programs installed then they will fight each other trying to tell the system if a certain file is infected or not. The system will not be able to make a decision. The system will just ignore both and let the file slide. Therefor causing a potentially infected file thru both your security programs and infecting your system.