I own a G17, 26 and a 21.
I had a G20 and G30 and a G22. Sold them all.
I sold the G20 after having some fun with it, decided there was no reason, *for me* to have a G20. Got out of it what I paid for it.
My first Glock was the 17. I just think anyone who wants to get into Glocks, needs to get the "original" Glock, the 17. Mine is a Gen 3. Has run without fail since day one.
After a lot of research and study, I decided to use a G26 as my EDC when I can carry it concealed, there are times when I must use only my Ruger LCP.
The G26, for me, is my favorite Glock: size, power, and capacity. I put a CT laser grip on it and carry it comfortable either IWB or OWB. I perfer OWB.
Glocks just work, period.
I love the G21, it is the one I'm most accurate with, by far. I tried the 30, but the 21 in .45ACP is the "most perfect" Glock for my hands, etc. Too big to lug around as a CCW, but love it.