I shoot SS minor with my STI Trojan 9mm because that is the gun I own. I can't afford another pistol right now and all of my other pistols are 9mm anyway so I don't have to buy different ammo for it.
But, if I were just starting out I would get a .40. You could use it for SS and Lim10 and shoot major with it. And ,if you reload, you can download and use it as a great ESP gun in IDPA if you ever shoot that sport.
To answer your question, I have seen a mixed bag of both .40 and .45. A lot of it is preference and/or convenience.