I think questions for grip/recoil management, reload and such depends on if you can get your hand fully on the pistols. I shoot the g19 very similar to the way I shot my issued g22 because I get a full grip on either pistol. Reloading is slightly slower with the g19 because of the slightly smaller mag caused me to index it differently. Something a little practice will solve, but it is different.
So for me it was a small but real difference between the two. Once I practiced with the g19 most of the differences went away. Switching for me was no big deal but I switched permanently. You know, the whole One Gun thing. If you are going to be switching back and forth it may be a larger problem for you.
If you are switching from say a g19 to a g26 where you can no longer get your entire hand on the pistol, then it will be a larger difference to your grip/recoil management and reload. The g26 wasn't just my pinkie finger hanging out. It changed the grip enough that I was changing the pressure of my support thumb on the frame. The made long range shots go slightly right for me. Again, it was a small but real difference.
Another thing to remember is that many inexperienced shooters have a large problem changing pistols due to not having a consistent grip, sight alignment and such on their full sized pistol. While many experienced shooters switch pistols often and don't have much change at all. So where you are in your development matters too.