I've owned a G27 for 4 years, in which time it has been my daily off-duty carry piece and my back-up piece. I shoot with it every month (minimum 150 rounds). It has never jammed, misfed, or stove piped on me. It is most definitely the most reliable gun I have ever owned & I am extremely happy with it. (7,200+ rounds )
My department carries the G23, I've only been with this department for 10 months (having transferred from another). I also shoot this monthly and as of yet, have had no problems with it.
As a primary/ back-up combination, you can't do much better. The 27 will accept 23 magazines, which is a plus.
My one recomendation is to forgo the standard plastic sights, especially if your agency uses the Safariland 295 holster. You can have the gun come equiped w/ standard steel sights or night sights (highly recomended).
I just recently purchased a glock 27 for an off duty weapon. I have been to the range with it twice. It is a great gun, never jams. The only thing I did was get the add on piece on the magazine because I have a large hand that way my little finger has a place to grip
I should've mentioned that in my post above. the 27 definitely needs the grip extension, which is a replacement for the floor plate of the magazine. The most common are made by Pierce Grips. One is just an extension, while the other adds an extra round making the 9 round mag into a 10 round (which I have on both mags). The +1 extension works great, but it makes it slightly harder to rack the gun until its broken in (still never had a malfunction).
I owned a 27... I had to put an extension on my mags. Great gun, put over 9k rnds through it never had a stove pipe or misfire or a single malfunction. Great back up/concealed carry. If I own another glock, any glock I am replacing the guide rod, putting a slide release extension and some good tritium night sights.
I have owned both glock 23 and 27. I liked the 27 with the extended mag(+1) on the base. After shooting it alot with a 23 mag in it I decided to just keep a 23 and sold the 27 to another cop. I figured with the extra length in the mad I figured that whats another inch on the grip and muzzle. Glocks are real excellent guns to own.
Noone likes the Glock 22 huh?? I have the 22 for my duty gun...and it fits my hand like a glove. I couldnt ask for a gun to fit any better in my hands. I guess the model depends on the size of your hands. I have shot the 27 and 23 and I like them all.