I have a Glock 27 and I love it. Its a .40S&W
Unless you're buying twenty boxes at a time the price difference between 9mm, .40S&W, .45ACP isn't going to be that big of a difference. If you can, go with something bigger than 9mm. Proper shot placement is key, however there's no real reason not to go with something with a little more power. The Glock 17's are great firearms. All of the Glocks are. Anyone that says different either hasn't shot one or simply has their head up their ass. They don't fit everyone's hands, but no gun does. You said you love it though so it obviously fits your hands. Go to the range and rent the same size in different calibers then make the call.