I currently have a Gen 3 19 and love it. I am picking up a Gen 3 17 soon. So it depends on what you plan on doing and what your are comfortable with. Do you plan on concealing, doing competitions... It just depends on the shooter.
I carry the G26 in Gen4 every day...it's my range gun, my CC, and my fun gun all in one. If I were to get another Glock, then I'd get the Glock 19. It's the midsized frame 9mm. Still small enough for carry but big enough to get a full grip on when reaching for it on the range. The G17 is the full size frame (similar in size to the 1911) with a longer 4" barrel for longer distance accuracy.
My suggestion would be to go hold a LOT of different guns....Glock, Springfield Armory, Smith & Wesson, Sig Saur, they are all very reliable and user friendly guns.
Good luck and make sure to post pics when you get it.