I am admittedly not the best shooter in the world, but after having not shot any of may carry guns since March or April... I went to the range recently, and shot my most often carried G19/3.25moa RMR first, keeping 7/10 in the black of a B8 @ 25 yards. I then took out my G26/6.5moa RMR and shot ten rounds with it, posting the same 7/10 rounds in the black with that gun. Shots were fired at a fairly slow pace with both guns, but full ten round strings, with a max split of maybe half a second. Acceptable performance for me, for my first 20 rounds at the range, cold and rusty.
I was actually surprised I shot the 26 that well at 25 yards. At longer range, I have to concentrate on my grip a bit more with the 26. Basically, the two guns are almost interchangeable to me. Especially as the distance to the target drops. I'm sure I am marginally faster on splits with the 19, but probably not enough to matter in a defensive context. Adding something like a Pearce pinky extension, or a factory +2 with some 3M grip tape gives me almost a "bobbed" G19, grip wise.
All in all, not bad for being super rusty. I practice some grip and manipulations, and dryfire at home quite often, but life got in the way the last few months, so I hadn't fired a gun beyond a single 50 round plinking session with my suppressed Buckmark maybe a month ago.
I'm glad I RMR'd a 26.5. I'm not sure if I'll bother with a MOS 26 at this point, unless a deal falls into my lap. That said, I'd have zero qualms with sticking a FCD plate and an RMR on an MOS 26.5. I have been tempted to send my other 19.5 off somewhere, have it milled, and sell off my 19 MOS. If I do that, I may get a 6.5 MOA RMR, or one of the new Trijicon optics if they pan out.