There's a thread over in Ammo about how accurate the Hornady stuff typically is. Worth trying a box or two.
I really like the USP45F. I'm a big guy with big hands (have had to give up on really nice XXXL motorcycle gloves when they didn't stretch enough in break in), and its size works perfectly for me. Mk23 is for cartoons. The 9/40 frame is great, but the 45 is just a little better.