If you are going to run the grip extension, then I am +1 for the G19. A slightly longer gun is going to mean slightly improved ballistic (probably not enough to even mention), but also a longer (read as better) sight radius.
The length of the gun is also not really a factor for concealment, since the length of the gun follows the length of your body. If you carry IWB, the slightly longer gun might also make it more "tuckable" since there is more gun to be secured in your waistline. The grip is what prints, so the shorter Model 26 grip would be slightly better, but this advantage is reduced to almost zero by the grip extension.
There is also the G19C, with the compensator cuts in the barrel & slide. I think this is a kinda neat option, but there are things to be aware of because of the exhaust coming out of the ports when fired. Flaming yourself and a possible negative affect on night vision are the two most prevalent. Not something that I see as necessary, especially in 9mm. Mostly they serve as a place for lint to collect
Good luck with your choice, and as always I would encourage you to invest in a quality holster and practice ammo.