Im just going to start with saying that I am no expert.
I love the 1911. It is my absolute favorite gun to shoot because of how it handles, the weight of the gun and the "smooth" punch of the .45. I also think the USP .45 is a nice gun if you like the .45 caliber.
Going back to the age old debate of 9mm vs .45 I would say that I would go with a 9mm for self defense because it carries enough punch but gives you the ability to carry more rounds. If you get a 1911 for self defense I would suggest you get some sort of high capacity magazine since the original 7 rounds can go very quick in a "hot" setting. Personally I would recommend getting the 9mm SIG P226 as it is a really well balanced gun (at least for me shooting with the left) and it doesn't really feel snappy at all.
As for rounds go, I don't think the standard hard ball that someone suggested is a good option. Better just get some hollow-point or something that will do good damage but not penetrate brick walls etc.
Again, I'm FAR from being an expert on the subject but it is a summary of what my experiences have taught me so far.
(Given the age of people on this forum I'm sure the .45 will have overwhelming support..)