Depends on what range you want to play. All of them are pretty good tbh. If you want straight up minimum ttk nothing beats the ag/m42. Otherwise the Turner is probably the best all-rounder (I personally use quick ads, detachable mags and a 3x on it though).
My personal list, playing on console, semi’s as my favorite guns in the game and like to play objective, which means that slow ROF guns with bad hip fire aren’t really an option (sorry Selb 1916 and Johnson):
Best all around semi: MAS 44
Best semi for larger/open maps: Karabin
Most versatile semi: Ag/m42
Honorable mention: Garand (not heavy load)
Semi I really want to like but only seems to work well in specific situations: Gewehr 1-5