I also use MSE, sadly none of them are perfect. I've found common sense and some basic internet smarts works better than anything to be honest. That said I've been using Defender and then MSE with nothing else since Vista SP1 and been virus/malware free. Prior to that on 95/XP I used Norton for a while but I realized that I wasn't getting viruses, but at the same time it wasn't detecting any...aka I wasn't introducing foreign elements to my system, so I just decided to save the system resources. I've only used Defender and MSE because they have a minimal footprint on the system and are integrated well into Windows, update with Windows Update, etc.
For more anecdotal evidence I've done troubleshooting on other systems and found viruses/malware. It didn't matter what they were using, I've probably found something present on every AV/Anti-malware program out there by now. I can tell you that only the active/passive scanning matters though. The definitions only help with removal/identification of specific viruses, only the ability of the program to recognize virus activity can stop a virus.
after running a few benchmarks with Microsoft essential it holds up great with AVG and Avira
however it lacks a few features like scanning email etc
Plus I find that MSE isn't as good for realtime blocking, phishing and prevention
nevertheless a good solid antivirus