Of those 3, I have only shot the USP, HK makes the most accurate gun (opinion, for me) ever. It is so smooth and no malfunctions. The only reason I carry Glock is because they are smaller, cheaper, and have nothing hanging out to grab or forget to grab when the SHTF. I'd love to try a MK23, but I think the only dif is barrel and ability for attachments
In god we trust, all others we monitor...