I use DIN for my mk4s MUCH MORE than I use ORTF. DIN is more focused and evenly balanced in most cases IMO. YMMV. I have the active bars, so I can easily run DINa/DIN/NOS/ORTF/WideORTF. I run mk4/DIN 99% of the time. And mk41/DINa 99% of the time. I can honestly say that I'm consistently happy running those configs. I run mk4/ORTF usually at stage-lip or onstage. This may sound weird, but when I had my MBHO's back in the day, I would run Hypers/NOS occassionally if I was pretty close and DFC. I need to try that with my mk41s. I bet it sounds good up close! Ive been meaning to run my mk4s/NOS too, but I keep my NOS bar in my mk41 bag for some reason
I used to run my mk21s/NOS. That seemed to be the best config for the mk21s the few times I ran them!
It really just comes down to trying them out and finding what you like best