I ordinarily consider a "winter load" the best all year 'round, but I might, given sufficient reason, consider a "summer load" in the summer.

I consider your question a very good one, but I think that it is difficult for most people, certainly difficult for me, to answer it competently without knowing results of gelatin tests, perhaps using the FBI protocol, which is probably one of the better ones, but so expensive that they are probably about the only folks outside of a few ammo manufacturers who do it.