My EDC is a G26 except in winter when I want the extra "punch", then I carry the G30.
I have small hands, and the G26 fits me perfectly! I know the criticisms out there (everywhere!) about my caliber choice, but shot placement is king!
That being said, Shooter13 is absolutely right: try both if you can (maybe rent at a range, or as a friend who has one to let you shoot it) and if the snappy recoil of the .40S&W is fine with you the go for the G23. If concealed carry is an issue, try the G27 on for size (subcompact, same frame class as the G26, but in .40S&W).
Are you married, any adults (or kids responsible enough to be trusted with a gun) in the house? If so, have them try it as well. What works for you may not work for them, and you don't want to force them to try to shoot a gun they cannot comfortably hold or competently use. Fine if this is not a factor.
AND if you prefer the .40 but would like to be able to shoot with the economy of a 9mm, you can get conversion barrel kits to allow your G23 or G27 to fire 9mm. The conversion process is as simple as takedown: remove magazine, empty and visually check weapon, remove the slide/barrel assembly as you would in normal field-strip for cleaning, install conversion slide and barrel as you would in normal reassembly, function check, load magazine and you are ready.
Just a few thoughts....