I have killed about 90 head of African plains game with my pre-64 Model 70 .300 H&H, using almost exclusively 180 grain Winchester Silvertips. It was overgunned for some of the smaller game (Thompson's gazelle, gerenuk, etc.), but it put them down very reliably without much meat destruction. My main concern with using more than one bullet weight would be shifting point of impact. If that could be ruled out as a factor, then by all means try several loads.

However, I can remember situations in Africa where I was stalking one species and came across another species of another size category (Hartebeest-Peter's gazelle) which was too good to pass up. Changing ammunition from a heavy bullet to a lighter one would ahve been difficult if not impossible.....and unnecessary.

If you're talking about hunting in the US, where you are unlikely to encounter such a situation, then experimenting with a lighter bullet could be useful.