That's tough... I'm between a Glock 32 or Glock 30... Both for the same reasons... Small enough to CCW comfortably, and can shoot a multitude of different cartridge.
I would most likely go with the Glock 32 Gen 4. I carry, go to the range, and do informal competitions (same style as IDPA, but just with friends). The 32 would handle all roles well. .357 Sig is my current favorite handgun cartridge for personal defense, and it's ability to shoot .40 S&W, 9x19, and .22LR make it very desirable for me. And the biggest reason, is I just shoot the gun better than any other that I'm able to easily conceal.