I find several ways to look at this:
Maximize MV, so lighter bullet to "make up" for the slower speed from the shorter barrel, which I would not do, or,
Seek the maximum bullet weight upon exit, which could be either shooting a mono of whichever weight or to shoot the heaviest bullet you are most comfortable with, or,
Use a bullet that you know will perform at any distance you would use it. This is my preferred approach. I am not a mono guy, so I use the 250 Partition in the 338 win. It is soft in the front and stays together, and it mostly penetrates straight and deep. The 210 partition is too short for me; I found it would almost always turn and shed the rear core. The 225 Partition is a good bullet, but I have found notably better penetration with the 250s. That could be both higher SD (if you find any value in oddball statistics) and the lower speed of the heavier bullet, or maybe the jacket is thicker in the 250.
Either way, I would use the 250 Partition with a 16" or a 26" bbl in the 338 win mag. The animals cannot tell the difference.