Over the years I've read a considerable number of gun writers who maintain the Hi-Power is an improved design over the .45. Setting aside the issue of calibers, I can offer no opinion as I am not mechanically inclined. But I do love the Hi-Power.
Concerning accuracy, my S&W K frame, M14 Target Master with 6" barrel is easily the most accurate revolver I've encountered. In the world of semi-autos, the H&K P7 enabled me to shoot with an inexplicable degree of accuracy (in my prime) getting 3 and 4 hits on top of each other. This was so startling I laughed out loud when it occurred. Today my shooting is more somber.
I've shown these before but here is the S&W and the H&K. The latter, depending on condition, is selling for 2 to over 3k.