I did a survey of some of the most experienced shooters/trainers I personally know and here is the question I asked them all.
Assuming you had to buy your own pistol and ammunition (type of your choice) for combined self-defense and self-defense range training use, which caliber would you choose, 9x19mm Parabellum, .357 Sig, .38 super, .40 S&W, 10mm or .45 ACP ?
I surveyed the following and their answer:
BJ Norris 9mm
Bill Rogers 9mm
Bill Wilson 9mm
David Bahde 9mm
Ernest Langdon 9mm
Frank Proctor 9mm
Ken Hackathorn 9mm
Larry Vickers 9mm
Mike Seeklander 9mm
Paul Markel 9mm
Paul Howe 9mm
Paul Buffoni 9mm
Rob Haught .45
Rob Leatham .40
Super Dave Harrington 9mm