Handling the pistols is nice, but never EVER go on this alone. I've seen plenty of posts by others saying how they "hated" the Glock grip feel... but after they actually SHOT the Glocks, they changed their minds.
So remember: Guns aren't all about feel... but how they SHOOT! If/when you can, at the least, rent the models you want to try first, and see how they SHOOT!
Yeah, Glock grips are a bit longer (front to back, lengthwise) because of the "hump" on the bottom, which is there because of the hole down there. The hole is there for one to slip their finger in and grasp the magazine more effectively, to pull it out in case it somehow gets jammed. Or others say it was put there because the Austrian soldiers wanted Glocks' original magazines to not fall out of the pistol when they hit the mag release button, because they didn't want the mag's getting lost in the snow during training or real combat. So, the hole is there for them to grab the mag from the pistol. Either or, those're reasons why it's there.
You can heat it up and push it in (I'd try this, but up to you), or you can send it in to get it professionally reduced by some other company... but it'll cost ya some money.
Glock is now coming out with "SF" models, but only so far they have been for two .45 ACP Glock models: Glock 21 (SF) and Glock 30 (SF). Hopefully they'll be doing more models soon.
SF = Short Frame - Which means that they do a "grip reduction" on these models in the factory, before they're bought. The grip "hump" is shortened in the back.
P.S. Remember: See which guns you SHOOT well with. Feel alone is NOT what I'd suggest when picking a gun; yet so many people always mistakenly make this suggestion to others. Not good, imo.
I had no problems shooting a G23 at the range, which was my first time shooting a gun, and first Glock, too.
I have bigger hands, most likely... but I've seen WOMEN shooting Glock 20's (full size models, and even bigger than full size Glock 17s!). Remember, it's all about how you SHOOT the gun, not so much how it "feels" in your hands. Leave the feely, touchy stuff for a nice girl you'll meet, or've met already.