Just wondering what version of Windows you are using? Mainly because it impacts whether you would use MSE or Windows Defender.
MSE is pretty good for Windows 7, but has been replaced by Windows Defender in W10 as they decided to build it into the OS. On W10 it is very good considering it is built into the OS and provides nearly no performance losses.
A third party antivirus suite partnered with Malwarebytes 3.0 will nearly always beat any free program, or any single third party antivirus suite without Malwarebytes 3.0. I personally run Kaspersky Internet Security 2017, with Malwarebytes 3.0, and have Windows Defender set to periodic scanning.
People do say don't have multiple antivirus suites, and this is true, but bear in mind Malwarebytes is not an AV suite. It is antimalware, antiexploit, and anti-ransomware.
Windows Defender periodic scanning is also designed to run alongside other AV suites for the record.
In terms of best free AV suite, many say Avast is the best available at the moment for protection, however it can hamper performance quite a lot. AVG is still pretty good, but it isn't as good at protection. It does however not hamper performance compared to Avast.
In short, Microsoft is pretty good, and there are good free options, AVG being the best probably, but nothing will beat a paid suite. My recommendations for paid suites would be Kaspersky, BitDefender, then Avira, in that order.