I went with a Gen 5 17. While I do have a gen 3 23 that I sometimes carry, I prefer the non finger grooved grip and slightly longer length on the Gen 5's grip. The extra 2 rounds and longer sight radius are a fair trade for being a slightly bigger pistol compared to the 19. In my opinion, if you can carry a 19 concealed, you can carry the 17. As far as shooting goes, I had a 19, a 34, and my new 17. I kept the 17 out of the 3, though I did like the slide release better on the 34(which you can get replaced on any other model). I didn't go with the mos model as I don't like to run rmr on my pistols, but it has the front slide serrations which is nice.
A side note: go with what feels better in your hand. The glock 20 and 21 don't fit my hands at all, but their compact counterparts, the 29 and 30, fit fine. Any of the 9, 40, 357 sig pistols also fit me well, but I like the full size 17/22 frame. Luckily the gen 4+5 glocks have changeable backstraps to help with fitment. And sometimes people just don't like the glock grip angle period.
A side note: go with what feels better in your hand. The glock 20 and 21 don't fit my hands at all, but their compact counterparts, the 29 and 30, fit fine. Any of the 9, 40, 357 sig pistols also fit me well, but I like the full size 17/22 frame. Luckily the gen 4+5 glocks have changeable backstraps to help with fitment. And sometimes people just don't like the glock grip angle period.