Statistically, it sounds like a sample size of only one, i.e. one incidence, two rifles, two hunters (maybe) being compared.... with apparently no consideration to:
= Variation in hunter field shooting ability
= Variation in will to live of the particular animal
= Possibility of the "poor" shot missing the "bread basket" and hitting CNS
.... the end result could be damn near anything.
I would personally opt for the 338-378 Weatherby (only 338 Weatherby cartridge I know of and always wanted one) however on a singular field hunting basis it would be no guarantee at all of any sort of field supremacy.
Now, with many buffalo harvested with each rifle, under similar circumstances (skilled shooters with no whimpy recoil sensitivity between them, "just right" bullet construction for each, and no CNS shots), I think you would see a fair difference in the average results regarding the animal's reaction to the bullet impact and the subsequent take down.
BTW,
"....the answer will be put on to this tread next Monday...."
Is that kinda like retreading a tire?