If you already have a USP45, then I would get the HK45. I have a USP45 V1 and love it, but it is just a tad to large for my hands. My USP9 LEM is absolutely perfect! I will be swapping out the V1 for LEM as soon as I find some LEM kits. I want to get an HK45 sometime, but not before I get my rifles lined out.