G*3 is about 20.00 bucks less. Most think the g*3 looks better then g*4. I own both and the g*3 do look better to me. A glock is a glock. Can't go wrong. Go for the .40,And pick up the 9mm barrel for it.So then you can fire both.But if you get the 9mm-.40 Will not work. As to be the .40 to .9.. And 40's and 9mm same price for the pistol.
And if your using it for ccw the g27 is the right size. Mag 9+1.