In pitting a 945 up against a 1911, I'm firmly in the camp of the 945 for reasons I outlined above. Now for an angle from the other side, just because it's fun to keep discussing these great pistols.
The 1911 certainly has it's share of talking points up against the 945. The 945 is great looking pistol and it evokes thoughts of a 1911, but it simply isn't one. We S&W guys often like to say that it's a "hybrid 3rd Gen crossed with a 1911" but I can't really say that's the truth... I think what we really have in a 945 is a pistol that looks more like a 1911 than a 3rd Gen does.
The 945 has basically ZERO aftermarket grip options. The 945 is larger in most every dimension than the 1911, and this will matter a lot to many different shooter's hands, especially if nothing feels more "right" than a 1911. The 945 doesn't share hardly any parts with a 1911, and if you tinker with your handguns, that is one of the most enjoyable things a 1911 brings -- the ability to personalize your gun with parts you like most. Certainly helps when you find some mechanical issues that need attention.
A big issue well detailed in this thread already is that 1911 magazines practically grow on trees while 945 magazines are scarce. 945 guys are in far better shape than S&W Model 52 guys for sure, but the 1911 magazine market is totally easy in comparison.
While I don't think it's a big deal... the 1911 is certainly easier to field strip, mostly because dealing with the (fantastic!) Briley spherical bushing in a S&W PC gun is a bit of an art. Like I said just above -- I truly don't believe this is a big deal, but we still live in a world where tons of people don't like a Ruger Mark I-II-III because they are convinced that it's "too hard to put back together after cleaning."


Just stating that if we are comparing the 945 to the 1911, this is only fair... the 1911 is easier to deal with for most folks in a field strip.
The 945 is very much -OUT- of production. The other very sad angle is that as each day goes forward, S&W basically knows LESS about it and how to help with it as their knowledge base on our favorite guns continues to grow toward retirement.
Yes, I would choose the 945 every time over a 1911 again and again, but there are still certainly many solid arguments for choosing a 1911 over a 945.