First off, welcome to HGF.
I have owned a G26 and currently own (and carry everyday) a G27. The 26 is easier and cheaper to shoot but the .40 has a tiny bit (WAR!!) more.
With the 27 you can get a 9mm barrel/mags and have both in one. If you plan to shoot it a lot you will like the 9mm. It took me a while to get used to the 40 in such a small package but I like the subsonic factory (Win. Ranger) SD rounds and I load my own and can keep the charge to a minimum. That makes it TON's more pleasant to shoot.
Hope that helps. YMMV.