I think that selection should primarily be guided by prospective usage; a single-shot calibre for shooting what: target, light & medium-sized game, heavy game, dangerous game?
I personally own several single-shot rifles: a 6,5x57R that I mainly use for roe deer, a 7x65R that I mainly use for mountain game (because of an extremely flat trajectory with light bullets), and I recently bought a 9,3x74R that I intend to use next year on red deer and maybe one day on brown bear.
As Fuhrmann and Luv2Safari already mentioned it in the above chain of messages, the 7x65R (bullet range from c. 120 to c. 180 grains) and 9,3x74R (bullet range from c. 180 to c. 300 grains) would be prime choices for hunting use.
Louis