Have you considered the Model 22? 15+1 and you get the power of the .40 in a concealable weapon. Personally, I'd go with the .40 over the 9mm but just my personal opinion.
It doesn't seem to bother the 1000's of local, state, and federal Law Enforcement agencies that have to qualify with it several times a year and depend their life on.
If you have any issue controling the .40 then by all means go with the 9mm, if you can shoot the .40 and control it then by all means go with the G27 (carry the biggest caliber you can control). My first Glock was a model 23 and I still love it, but carry my G27 daily. The G23 was a great first gun because it was my carry gun and my IDPA gun (funds were tight back then and the size allowed me to do both).
I own a 23c and love it. I have held a 27 never fired but a clip/grip extention will be neccesary on either one. I dont mide the kick of a .40 so I would go that way. I havent priced 9mm ammo in awile but I can pick up 40 all day in NW OK for around .30 a round at wally world