I assume your wife isn't on AH? I mean....you just referred to her rifle as "your rifle".I have used a .375 a fair bit over the years. 2019 was my first experience with the 9.3x62. I am the first to admit that my data set is limited, however I honestly couldn’t tell the difference on buffalo.
My .375 is shooting a 300 gr A-Frame at 2500 fps.
My 9.3x62 is shooting a 286 gr A-Frame at 2400 fps.
I wouldn’t consider either a good choice as a charge stopper, however either appear up to the task for a well placed first shot on buffalo.
I personally shoot a .458 Lott for buffalo, but as to legal minimums on DG, I would think that inclusion of the 9.3x62, 9.3x64 and 9.3x74 as legal DG calibers in all countries would make a lot of sense.
My 9.3x62 (Rigby Highland Stalker) is a much more manageable rifle for my wife.