What do you want it for?
I guess I'd vote for the .45 simply because it's more "classic"
For the record, I am one of those weirdo's that prefers the .40 recoil to 9mm. Everyone complains about the "snappy" and I'm shooting 9mm and singing "whip it! whip it good!". I like DEVO as much as the next person, but not that much.
So you won't hear me giving crap about the caliber.
But I also really like .45's, so there you go.
The one good thing I will note about .40 S&W, that hasn't already been mentioned, (and this also goes for 10mm) is that when there is panic ammo buying going down, it's generally one of the last calibers to completely disappear from the shelves. In fact, during the worst of the last panic, it never disappeared around here.