I don't know that I would want to use any of the ones you listed for "combat." To me a combat weapon (something the military might use) should be easy to maintain, easy to find parts and ammo for, and not so big or powerful that they can't be used comfortably by most people. The Desert Eagles are cool (I've shot a .50 and it was awesome) but they're not known for reliablilty. The Auto-mags are probably the best large automatics but they're extremely hard to find (I've only actually seen one out of the dozens of gun-shows and scores of gun-shops I've been in) and the ammo is not something you can buy at wal-mart (or most most gun shops for that matter). I think the .45 acp. is probably the best all-around combat pistol round preferably shot out of a 1911, however H&K, and SIG also make good weapons.
As far as .44 mag. "snubbys," S&W, Colt, and I believe Taurus and Ruger make them with a 4" barrel. Taurus makes a .44 special snubnose but I don't know of a .44 magnum that's any smaller...not that I'd want one, the recoil in something that small would be almost uncontrollable.