User Activity

I just upgraded 5DM3 to a 5DM4 ... but when I installed DPP 4 it seems unwilling to process jpeg.  IT shoots RAW and JPEG fine, and I get both in file at download.  I still have DDP 3 installed tho altho I seems unable to open RAW from 5DM4 Sometimes...
I've been using 5DM3s for years - and am thinking upgrade time.  My delimma - do I go to 5DM4 - OR - what is the benefit or not switching to Mirrorless. I shoot sports and action wildlife ... so lenses  ... 24/105, 70/200, 100/400  and they get used ...