The weight. I knew I wanted a sub compact and thought they were mostly the same but they are not. Loaded the G30 weighs 34oz and the G27 is 26.8oz., big difference if you’re going to carry it all day IMHO. I do recommend the sandpaper decal grips, they really help. Especially if it’s humid.
I can see where it could get heavy it you carried daily or needed “real” concealment. I sometimes grab the 30 and just drop it in my jeans pocket (I don’t chamber a round) when I go to the farm or ride my motorcycle. It has come in handy a time or two.