They have been bringing in Bar-sto G19's at one of the shops here in Vancouver and I have handled them there a few times. I've also fired 10 rounds a couple of times through a couple of different G19s owned by other members of my range, including a Gen 1 G19 prohib. I own the G17 and am happy with it. I find myself moving more toward SA/DA pistols these days, but for what it is (a "bomb-proof" DAO that requires little maintenance, is easy to strip and clean, barrel cleans out very easily, will virtually never fail to go "bang", is as accurace as it needs to be, and will give you very few, if any, problems over its life) the G17 is a sure bet. The G19 is the same gun. It's just a half inch shorter off the front and a half inch shorter off the bottom. The half inch off the front is easy to engineer. The slide, the barrel and the frame are all just that much shorter. A G19 in the U.S. is 102mm (4 inch). A G17 is 114mm (4.49 inch). In Cananda, for legal reasons, we have to tack a extra 4mm onto our 4 inch guns so that they are longer than 105mm - hence the 106mm Bar-sto barrels.
Taking a half inch off the bottom of the grip is a bit more tricky. The way they did it (on Gen 3 models anyway) was to "condense" the grip pattern down a bit, get rid of that open "half moon" shaped thing at the front of the bottom of the grip on full size Glock models (you should be able to see what I'm talking about in many pictures of Glocks), and then make the bottom of the magazine sit more flush with the bottom of the grip than on a full-size.
I'm a large person (6'3", 215lbs.) with average size hands for a person of my size. When I hold a G17, the bottom of my palm is right at the top of the "half moon", i.e. it is not hanging over at all, but there is no more grip if I were to move my hand down. When I hold the G19, the gun - magazine and everything - ends at that same place... the top of the "half moon" on a G17. When you look at a G19 you will see that the front of the magazine sits flush with the front of the grip, or at least a lot closer than with a full size Glock. In my case, on a G19, the very bottom of my hand is just sitting comfortably right on the front of the inserted magazine, but there is no gun at all beyond that (unlike a G17 where there is that open "half moon" area and the bottom of the magazine under that - none of which your hand sits on anyway).
Hope that helps a bit, if you haven't handled both guns. I find the G19 to comfortable to hold and you don't lose anything over the G17. Most of what is taken off the bottom is surplusage in my view (other than that it is a little more unforgiving to get the magazines in on a fast, IPSC-style reload). Some people just like the feel of a 4 inch gun more. A 4 inch gun can give you the perception of less barrel flip, but this is probably mostly just perception. (9mm guns are easy to control anyway if you hold them right.
I'd say go for either. The thing with G17's is, if your range is anything likle mine, you will never go there when there aren't at least a couple of other people shooting a G17 - many of which are people that have just gotten into shooting and bought one as their first gun., which is cool. We've all been there. G19s used to be a bit more "cool" and "oooh" because they were less common. I must say that, now, in the Questar age this is increasingly not the case. I've been seeing lots of G19/23 and G26/27 lately. They're everywhere.
Is the G19 worth the extra $400? No, absolutely not. As I say, it is not a different gun. It's just a half inch off the front and the bottom. That's it. But, having said that, I am going to buy one myself... just becasue it is still pretty damn cool, and just for those intagible reasons why people buy multiple guns of similar styles. But again, having said that, I'll be buying a USP before I buy a second Glock.