Something that hasn't been mentioned yet regarding "which Glock to buy"
The OP is really getting a lot of sound advice from a lot of experienced and knowledgeable people, every one of which I'm guessing knows more about guns, (and Glocks in particular ), than I do; however, there are several more factors that no one so far has mentioned. I was in almost the same quandary about a year ago as the OP is in right now; I had originally just about decided to go with a .40 cal. G-35, but after doing a LOT of reading and shooting various different peoples .40s and 9mms, I finally decided to go with a 9mm. I had even given a lot of thought to buying a .40, then getting a Lone Wolf 9mm barrel for it and have the ability to shoot both calibers with the same frame; Here's a fact that several people have already mentioned........if you think there's any chance that you may at some point in time want to get a second (and even a third barrel ).....you MUST start with a .40, then you can use a 9mm barrel with it, (and also a .357 Sig barrel ), however, you CAN NOT go the other direction, and use a .40 barrel with a 9mm model; (something inside isn't wide enough. )
You may have noticed (like I did ), that Glock makes about 26 different semi auto pistols; being a naturally curious person, any time I have a LOT of "choices", I like to explore ALL of them prior to committing a sizable chunk of $$$$. One of the best small investments I made while evaluation everything Glock makes, was a copy of the 2014 Glock Buyer's Guide; after studying that book for a few months, then talking many times to a very knowledgeable young fellow at a LGS (local gun shop), I realized that for exactly what I wanted a Glock "for", I need a G-34 instead of a G-19 (4.01 inch barrel & a capacity of 15+1 ), or even a G-17, (4.48 in barrel & a capacity of 17+1). I decided I wanted to go with the G-34 which has a 5.31 in barrel, plus a 4.5 lb trigger rather than a 5.5 ib. (The G-34 also has steel sights rather than polymer. )
If you have ever watched Team Glock's Tori Nonaka blowing the competition away with her long-sight-radius G-34, you'll know why I didn't want a 4 inch barrel.
At this point, I was ready to "write a check" and get exactly what I wanted! Then I had a very fortunate "accident"; I had run into a Wal Mart for "whatever", (and I can never seem to get out of a Wal Mart without first checking out all of the new gun magazines ); Fortunately, Glock's new 2015 Buyer's Guide was on sale; (another $6.00 well spent! ) Only this time, it wasn't a new gun that caught my eye, but rather a "modification" to several existing guns (plus the all-new Glock-40 in 10mm). Glock had just announced that the G-34 (9x19), the G-35, (.40 cal), the G-41 (.45 cal), and the brand new, G-40 (10mm) were all four going to be coming out as "MOS configured", (MOS meaning "modular optical system); I had already read quite a bit about "red dot" (or "reflex" sights), and I knew after reading the story in the 2015 buyer's guide that I needed to wait for my LGS to start getting the 20 MOS Glocks that they had on order. This was all months ago; I even started a thread here, to see if anyone had any more info on these new models with their slides milled and the necessary mounting plates for attaching about half a dozen different red dot sights.
There IS one thing to "not like" about Glock, (the company); their so-called "customer service" rarely, (if ever), renders any real "service" to their "customers"! (An email to Glock CS got me a very brief, "we only ship to our "distributors" so you need to speak with "them"! ) (Like I'm supposed to know who (or where) Glock's "distributors" are? ) Anyway, once I had my name in for the first new G-34 MOS to get delivered to Terre Haute, I always take the wife to a steak joint right down the street from the LGS every Wednesday, so I now have a convenient excuse to "stop by" the gun shop to "check on" the new Glocks! Last Wednesday they surprised me.......10 were delivered that same morning! Not having "quite" the cost of a new Glock in my pocket, (and preferring make ALL LGS purchases with cash $$$ ), I put the G-34 in "lay-away" until this Wednesday.
It all depends on what you want the gun for; and there's a pretty safe bet that "what ever" you want it for, Glock probably has a model that's "perfect" for the task! (I'm aiming that remark exclusively at "Glock aficionados"! )
If anyone wants to start a new thread about Leupold. EOtech, Doctor, Aimpoint, Meopta or Insight and several more makes of red dot sights, I'll see you there, as that's my next decision to make.
BTW.....if you're curious to see what Glock's premo target model looks like with a Leupold Delta Point mounted to it's milled-out slide, check out any Wally's World magazine dept for the current issue of "Modern Shooter" and there's a G-34 MOS on the front cover. (I'll bet Glock's "customer service" will love that!)
While I was at WW, I also ran across a copy of Richard Mann's "Handgun Training Training For Personal Protection". It's not germane to the present topic, so I won't discuss it other than to say, as it was the only thing I had with me to read on a 5 day trip to N. Illinois to visit family, after I read it through several times, I feel that it has already paid for it's self and I would recommend it highly, (even if the author does admit that "he hates Glock pistols") after carrying them for 13 years while he was a LEO (and didn't have a choice ).
Anyone who is convinced that "this caliber" is more "deadly" than "that caliber" seriously needs to read what this highly experienced guy has to say on that subject.