I've carried everything from a Kimber Pro Carry, Glock 19, Glock 20, S&W 1006, Springfield XD45, Witness 10mm, Kel-tec P3AT and PF9 and everything seems to come back to a DAO mid size semi auto as my favorite.
During the cool season I use my XD-45. Summer time has recently been taken over CCW duties to the PF9 for now. Out in the bush, its my 10MM Witness.
For me it depends on what I'm doing that day. But for the last 3 years it has been my XD-45. Now that I'm back in Arizona, Its too damn hot to wear an undershirt so I went with the pocket carry PF9.
I think it takes a CCW carrier several years to find the one that they like the most. As you can tell by what I've carried, its still a work in progress.
Find the gun that you like the most, give it a try and see if you are comfortable with it. What we like may not ride right on your body, feel good in your hands or is available to you. On that note, carry rigs make a big difference as well. I probably have at least 50 different hosters in a box that I've tried.
Good luck on your quest for the perfect CCW platform.
If you see a Military man or a Vet, stop him and say "Thanks".