nxview is a tool specialized in picture management. MC is more of a generic tool for all kind of file management. A tool that specialized in one area is already going to be better in just that.
But comparing MC with xnview is not really fair
xnview is a commercial product that cost money. They have a lot more resources and time to spend then me.
MC is free and is developed by me alone when I have time over. So sorry. I can't spend the that amount of time it would require.
I have to really prioritize what to spend time on, spend 5-6 month on 3-4 new features and bunch of fixes. or improve something that not many uses and that works okey to make it work extra good. Sorry....