G'day Shane Justice, and et al.,
Interesting selection, all are good enough for the task. Since you've specified the caliber, your declared variable is size. Of the three that you mentioned, you've basically listed small medium, and longer barrel lengths. NOTE: the 17 & 34 share the same frame, so the grip is identical, only the barrel and slide length are the differential factor.
Hope that added information will help. If you'd like more specifics, you can always reference other Glock type web sites. I've found Glockmeister to have a very nice presentation of information. If you'd like have a go at:
www.glockmeister.com
Now if you're interested, please allow me to opine regarding my experiences. Glock has three frame sizes for the 9x19mm, they produce the 26, 19, and 17/34. I've owned one of each size. Yes, they all shoot well, they all fit the same holster and magazine holders too. I've found over the years that both the 26 and 17 fit my hand better, thus a more natural comfortable, and quicker shooting characteristic. NOTE: these are both subjective observations base on my personal feedback combined with objective measurements using a shot timer. Yeah, I've made many runs with each platform on plate racks and monitored my times using each. With that information the 26 and 17 have been used quite a bit for both serious and casual applications. The 19 has been traded off.
Hey, what ever you choose you can always use some of those G18 mags for some range fun! Best of luck to your quest for your acquisition effort. Try'em and buy'em! Cheers!