agree the H&K USP compacts arent very compact, a glock 19 is smaller, and a glock 19 is imho at the very top range of being small enough for edc, oh sure with a good holster/bely combo ya could do it but its not gonna be pleasant to deal with daily.
if ya want a .45 a compact 1911 would be ok, or the single stack glock would be better, or the kahr P45 would be the best imho.
imho a kahr P9 or PM9 is a lot easier to deal with daily and 9MM works just fine with good ammo, if ya just gotta have a H&K the P2000 9MM wouldnt be too bad but its not nearly as easy to deal with as the kahrs.
the kahr .40's are also good but imho the ammo is so close it doesnt offer any great advantage over 9MM, as long as ya are talking good ammo ie speer gold dot, w-w ranger, etc.
i live in TX and edc a pistol daily and its been my experience that smaller is better as long as its a service calibre, reliable, and accurate enough, and i suppose as long as ya can shoot the thing lol.
i have edc'd 1911's, SIG P220 & P225, barretta 92, glock 32C, 17, 26 & 33, and a couple of revolvers and other than the glock 26 and 33 they are all just too big or too heavy (or both) for dealing with daily, it can be done with a good holster/belt/the right clothes but it quickly can become a PITA to deal with on a daily basis, especially in the summer, the kahrs are by far the easiest for me to deal with, and are plenty reliable & accurate, and fire an acceptable cartridge.