A toss up between my 29.4 and 26.5.
The scales probably tip in favor of the 26.5 because of the flexibility of different mags, 10-33 rounds, that also fit my AR pistol.
I don't own any Glocks, (yet) but if I could only own one, then it would probably be the Model 32 in .357 SIG, since it can be converted with ease to .40 S&W or 9mm Luger.
Currently, the closest thing to a Glock that I own is a S&W Sigma SW40VE, which is a clone of the Glock 23, but I really like it and it serves as my primary EDC pistol.
As I only own one Glock this is pretty easy. The Glock 32 Gen 4 .357 has proven to be reliable and accurate. I like it more than I thought I would. The only thing I’ll be changing is the plastic sights for a more durable set of night sights.
I have a Glock 29, just because I wanted something in 10 mm and at the time Glock was just about the only choice. I also have a Glock 44. It's like the perfect sized gun so The One would have to be it's big brother, the Glock 19.
For me it's the Glock 48 for one simple reason: It fits my hand while no other Glock does. I carried a Glock 22/23 as a issued duty weapon for my career and always struggled with the grip size. I would prefer it to be .40 S&W but that will probably never happen. For those whose hands accommodate them another Glock with higher capacity will probably be a better choice but I really like my Glock 48.