I'm sure the Barnes TSX in 338 is a great bullet, BUT if these are the only factory loads available then I would have serious concerns about recommending the 338 for Buff over the .375. IMHO if you are going to go the .338 route you need to find someone to handload for you with (preferably) the 300 grain woodleighs. If you don't have alot of experience with either buffalo or harder recoiling rifles, and are only going to shoot buffalo occasionally, you could be asking for trouble - gaining experience the hard way

There MUST be heavier factory loads available somewhere, even if they have to be specially ordered for your buff hunting trips. The range of Winchester and Federal loads available will be great for all your other hunting though and great for pigs. JMHO