I'd agree with most posts above...
1. A-10C: easier to fly, but more complicated avionics, more weapon diversity. You have to learn to drop various bombs and that takes time. Learning the CDU navigation in depth also takes time.
2. Ka-50: Much harder to fly effectively, takes more time to get used to it, has somewhat simpler and old avionics (although the ABRIS also has loads of functions not a lot of DCS pilots bother to learn). The weapons employment is somewhat easier, but cannon employment requires finesse and careful piloting, which takes somewhat more time than in the hog.
Overall, YMMV I guess. Depends on your style of flying and approach. Reading the manual and having a good instructor speeds things up immensely.
I'd say start with the A-10C and work from there. Once you learn the A-10C, the Ka-50 will be much easier for you, I guess.