The answer to your question, and some you didn't ask:
While looking over all the HK choices, I compared many of them side by side.
The USPc has a noticeably slimmer grip than the USP. The grip of the USPc is about the same width as the slide, while the grip of the USPf is thicker than the slide.
The USPc 45 has a SLIGHTLY (barely noticeable to me) thicker grip than the USPc 40. I would close my eyes and pick one up, then the other, and couldn't tell a difference.
The USPf 45 is bigger than the USPf 9 & 40 to about the same extent that the USPf 40 is bigger than the USPc 40.
With the USPc extended baseplate, the USPc is about the same height as the USPf 40.