As a median average it's whatever pistol size you are most familiar with that's going to do well for you.
I've often thought about this very topic while waiting for my turn on the line. The conclusion I've reached is that Glock compact frames can be made to shoot well; and, yes, they do seem to be a little faster out of the holster; but so what?
Glock standard frames shoot and handle well too. I, myself, prefer to use a G-21 (power factor!); and I've no compelling reason to change. Sometimes I use a G-19; and, yes, I've got to be a little more careful about pointing the muzzle, watching the front sight, and pulling the trigger than I do while I'm using the G-21. It does take a little more care, and a little more concentration to skillfully handle a compact frame.
A few years ago one of the finest pistol shots I know switched to a long slide Model 35. Why did he do it? He did it because it's the longer shots that he's going to beat the rest of the group with. Several other competitors have a similiar ability to hit at and inside 12-15 yards in the same way that he does. It's only on the 15 yard + plus targets that he can really pull away from everybody else. Hence, the G-35!
Glock G-34's and G-35's use a (nominal) '3.5#' trigger connector which does yield a somewhat lower CUMULATIVE trigger pull. What a, '3.5#' connector will NOT do is yield an actual 3.5 lbs. trigger. Whenever you want to determine a Glock's actual trigger pull several other factors need to be taken into consideration besides only the connector's cantilevered top angle; e.g.: trigger spring, recoil spring, and striker spring weights. The connector angle, itself, is not going to give you a specific trigger pull weight.