I would try the Sierras first. If you find a good load for them (and in my experience you will) then the Partitions will probably shoot well with the same load, and probably to the same place. Then he can sight-in and practice with the Sierras, and use whichever bullet seems most appropriate for whatever game he's hunting.
The Speers might even shoot to the same place, with a little experimentation with the powder charge. All three bullets will easily kill deer, but in my experience the Partitions will exit more often, but that doesn't mean they'll kill any better. The Sierras may end up being the most accurate, but probably not enough to make any difference in killing big game.
