I have the USP .45, and it is right at the ragged edge of 'concealable'. It is truly big. Think full size 1911, but with bigger grip. The compact .45 is smaller. That said, I think the USP 45 is a really good gun. Honestly, I use mine at the range, and as a "Dinner gun" - since here in VA we have to open carry in ABC restaurants, no need to bother trying to conceal it...
The Para will be a bit heavier given the all metal construction. I don't think prohibitively so, but something to consider.
Defer to the glock-o-philes on the g30. The .45's of this breed don't have the same following, I'm not sure why.
One thing the H&K has is that you can reconfigure it - DA/SA, cocked & locked, decocker only or LEM / DAO.
FWIW, I have 4 other .45 ACP's, 3 of which may be carried concealed. They are:
EAA Witness full size - Inexpensive, reasonably accurate.
EAA Witness compact - as above.
Both do not have a decocker, which I prefer. Also, it's possible for me to insert the magazine to both hard enough to prevent the slide from going forward.
S&W 325PD - wheel gun, very light, stout recoil, but a nice, accurate and reliable piece.
The H&K is easily the most mechanically accurate of these from my observations.
HTH