Whichever rifle is the most accurate and the one you shoot the best, only way I'd pick the 300 WM is if heavier plains game were on the list.
150gr in the 308 and 200gr Partitions in the 300 WM are tailor made for this, you'll quickly blow the front core in the near shoulder, tiny hide kind bullet shanks will exit offside on both.
Used my 400 H&H as a light rifle for all Tanzanian plains game, coupled it with a 577 double, wanted it for Buffalo and dry land Hippo, it's loads were 400gr A-frames and CEB #13 solids, they both left at 2400 fps over Varget.
Knowing Leopard was on the list, and also knowing you can't shoot a cat too fast, having only a 2400 fps start speed with the very tough 400gr A-frames I had to improvise.
Filed off the tiny lead meplats on the 400gr A-Frames down to the copper jacket line, hit flat with a center punch, sent a 1/8th drill bit dead center down into the lead core one quarter inch deep, chamfered hole and went to the bench.
Happily discovered they landed in the very same spot at 100 yards with the unaltered bullets.
My shot came at 77 yards from the blind, the old Tom dead bounced off the ground from a double shoulder punch and slid down the bank of the dry river bed, so even heavier caliber medium bores at sedate velocities can be made to work, your rifles with Partitions at greater speed will be perfect, imho.
