It really depends on what type of shooting you'll be doing, and what gun you choose for given competitions...i.e. do you want to compete IDPA and shoot a Single Action revolver? Or do you want to compete in Cowboy Action Gunfighter Class's, or maybe Single shot silouette?......

I'm assuming that you're looking for an auto pistol to compete in action shoots, as are most people who ask your question....I'm going to suggest you go to a few shoots, check out everyone's equipment, ask to try out a few guns, maybe hook up with an experienced shooter and try to borrow one of his guns if he's got an extra....that's definitely the best way to get into this game.

You could always just buy a Springfield 1911 in an upgraded model, or a top of the line kimber and enter in stock pistol categories until you get the feel for what you will want to upgrade to, or how you want to alter your pistol...at least then you'd be getting the experience of shooting, and the advice and observation of seeing what everyone else is shooting before you dump $3000 on a gun that's not right for what you need, it's always handy to have a stock .45 around anyway.

How experienced of handgunner are you? If you're just starting out with handguns, it might suit you well to try out a .40S&W instead of a .45acp, still a big bore and people won't mock your tiny 9, but it's not quite as abrasive as the .45acp.