I stepped into Glocks slightly backwards compared to most...
I purchased my first Glock, a second generation Glock 21, in early 1991. Some people were reporting problems with the early mags failing to feed some .45ACP hollowpoints (even though the one that I had was doing all right with Speer 200gr 'flying ashtrays'), so I sent back all my mags to Glock and they replaced the followers and springs at no charge to me (except for the postage to send the mags to them, of course)...
I liked the Glock 21 so much that I turned right around and picked up a new Glock 17 (also in 1991), also a second generation gun.
My brother has a second generation Glock 19, also a great gun.
The feel of any handgun in the hand is somewhat of a personal sort of thing. I have pretty big hands, and the second generation Glock 21 feels good in my hand. The second generation Glock 17 has never felt quite as good because it swells on the backstrap right in the wrong place for my hand. It's still not bad, but not quite right. The second generation Glock 19 feels perfect in my hand. As a matter of fact, I liked my brother's second generation Glock 19 so much that I finally decided to pick one up for myself. Being a little smarter these days (yeah, sure...) than in the past, I actually went to a shop and handled the new 3rd generation Glocks before I ordered one...
What I found was that the current generation Glock 19 frame with the finger grooves on the front strap doesn't feel anywhere near as good in my hand as the second generation Glock 19 does...
But I found that the current generation Glock 17 feels really good.
So I decided to get a current generation Glock 17 instead of the Glock 19...
All's well that ends well...
Forrest