Public companies have their books audited by external entities to ensure impartiality and objectiveness. Microsoft writing its own anti-whatever fails that test. It is also so typical of Redmond to whine whenever anyone criticizes them. So what if the AV test people run a harness that covers everything? All MS competitors' offering faced the same test, except they passed.
I run Norton 360, have done for years, at $60/yr for 3 PCs it's a bargain. None of the issues of false positives, verbose updates etc. that others on this thread report. You get what you pay for, which explains why the MS protection software is free.