As stated above, try to rent or borrow what you are considering, then decide. I won't tell you which is the best, but will say that you can do a lot worse than any of the fine pistols you mentioned. Besides, best is relative to YOUR individual needs. I've have had or currently own all of the above so Ill just offer some general impressions:
Sig P220 - nice feel, liked the weight because it felt solid, did not like mag capacity, stock sights decent, despite things I've heard never seen a rusty Sig (although I don't proclaim to have seen it all)
Glock 23 - excellent all-around pistol, as far as reliability, accuracy, durability, concealability, and capacity; trigger has a different feel but once you get used to it, it feels normal; love the "safe-action" system; simplistic; good weight even though polymer; replacing stock sights necessary for me; hi-caps are expensive but worth it to have at least a few; castrated 10-rounders still hold more capacity than most 1911 style pistols
HK USP - solid pistol but big; trigger less favorable after I got use to the Glock; mag situation same as Glock; definitely harder to conceal unles your are of a large frame
1911 - an all-around classic and very sexy; tunable to the nth degree if you like to tinker, though minimal customizing can result in a fine weapon; if capacity is an issue, options for hi-cap mags/frames are Para-Ord, Kimber polymers, Wilson Combat's polymer (though the Wilson is only 10 rds, and not truly hi-cap). Then there are other more exotic creatures like Caspian, STI, etc. Trigger is in general the most crisp of the four pistols you mentioned, for obvious reasons.
These days, I tend to gravitate towards Glocks and 1911s - Glocks because it fits me the best in all that it offers; 1911s because, like I said, they are just sexy, and yet still make a damn fine weapon. However, I would not hesitate to own any of the ones you mentioned if funds were unlimited - I have just prioritized my wish list.
It comes down to what characteristics you value most, what you already have in your arsenal, and the primary purpose of the weapon of choice.