That's a loaded questions with a lot to answer. The Colt Python or Colt .45 (I'm assuming you mean a 1911) are your best choices. The Desert Eagle is ridiculously expensive and a behemoth of a weapon. Since the Python is no longer in production you will have to find a used one, but they will be pricey. A "reasonably" priced Python that still works and is pretty to look at will be just north of $1000. The benefit of having the Python is that is is chambered for .357 magnum, which means you can shoot the lighter recoiling .38 special through it too.
The 1911 will be more prevalent because everyone makes one. Small parts quality is a major factor here and most people who espouse how great their Kimber or whatnot is overlook the fact that all their internals are going to be garbage. That being said, I highly recommend Colt as your first choice in a 1911. They make the best ones in their price range, plus it's a Colt. Springfield Armory also makes an excellent 1911 and would be my second choice. Realize that a 1911 is not an ideal choice for a beginning handgun shooter. Field stripping is more complex than modern semi-autos, but it's still relatively simple. Maintenance is no more strenuous than a modern handgun until you start getting into higher round counts. Eventually parts will need to be replaced. The extractor is a big one, and many parts like that require fitting on a 1911. Unless you are comfortable and capable of doing that, you will have to send it to a gunsmith.
Ammo for both the Python (.38 Special and .357 Magnum) and the 1911 (.45 ACP) can be found at any sporting goods store, gun store, wal-mart, etc. Ammo for all 3 calibers are similarly priced.
What do you intend to use this gun for? What made you choose these guns? I can think of several choices that will probably better suit your needs... without even knowing what those needs are.
Additionally, make sure you buy yourself a decent holster. I originally came on here to post this article, but though I could kill two birds with one post.
ETA: Looks like ExBoneOSO already posted the article in the WTF? thread... Police urge holster use after man shoots his own penis.