Gotta agree with Hendrik. Windows 10's Windows Defender over the last year to a year and a half has made leaps and bounds from where it used to be. They've been integrating new security features which puts it on par with paid anti-virus applications. Yes, Windows Defender *can* mess with Media Center, but it's very easy to tame so Defender doesn't mess with it if it does indeed mess with it. There are some users who have never needed to tame Defender since they don't encounter any issues with it and Media Center.
It's kinda sad to see these third-party anti-virus applications becoming more complicated and convoluted while doing things they really shouldn't be doing (e.g. Bitdefender DLL injecting and causing ntdll.dll crashes in multiple applications). Some users may recommend to use Windows Defender alongside another standalone application, like Malwarebytes Anti-Malware, but even that has declined in quality and increased in complexity for an on-demand scanner for me to even recommend anymore.
It's funny, I remember not too long ago Windows Defender was treated as a joke (which honestly it kinda was). But I have to give Microsoft kudos for improving it significantly and taking security seriously.