We like to think of these things as clones, duplicates, but they are built within tolerances, parameters called "acceptable". A lemon is always a possibility, but of the Glocks, G30 is one model that gets few complaints. Conversely, the G36 seems to be a fussy little bugger! Kind of like Volkswagens--get a good one and you'll love it!
I've rented a G30 on two occasions, putting 200-rounds through it both times. Each time I was impressed, and by my last box of ammo, I was shooting the little gizmo about as well as my G21, which is to say, pretty well!
The rental unit was a 2nd Gen G30 with two magazines, one having the Pearce Extension. This would be a must for me. I have fairly big hands, and long fingers, so the blocky Glocks feel good to me, and the magazine extension made it just right.
The G30 was originally introduced as a "Compact Model", as was the G29. It has a rail for a laser or weapon light, and for all practical purposes will do what a G21 will do, less a few cartridges. It will conceal on a bigger guy. There are plenty of accessories for it.
The G30 was my next planned purchase, but I'm going to wait to see what our goofy state does, since they're frantic to disarm us. .45 ACP ammo has gone way up in price, and is often not available.
I've only held the G36, never fired it. The slender .45 would make one hell of a BUG! Assuming you get a good one. Accessories for this model are slim, as compared with the G30.
You may want to hold out for the G30SF, which is confidently expected by February of 08. This will offer a slimmer grip than the current G30.
--Ray