I really like QGroundControl - have gone to using it pretty much exclusively. Mission Planner's one downfall is that it is not cross-platform.
Windows used to be the most popular personal computing platform and MP was developed for it, based on that fact. That is no longer the case. Android (which is based on linux) now holds that crown by a huge margin. More and more people continue to move to mobile computing platforms. So I see MP as eventually having to evolve, as being stuck on Windows in this day and age is pretty much a dead end street. Windows is still strong in the desktop computing space, but fewer and fewer people are using that anymore when we now have cell phones that have more computing power than most consumer PC's.
I had a Windows 10 laptop here that our daughter gave me because she got a new Mac. I was going to put MP in it. But I couldn't figure out how to use it because it thought it was smarter than me and constantly wanted to do different stuff than what I wanted it to do. I finally fixed it. I put Ubuntu 16.04 linux in it and it's been working fine ever since. And I have MP running in it with mono, but I only use it for reference now and then.