I seem to recall reading that one is more temperature sensitive than the other. Can't say for sure. H4350 seems to be more popular in some circles.
I've used IMR 4350 in the 6.5 CM with no issues, but haven't had the chance to do any real comparisons between the two powders.
Paul
IMR4350 is usually quite a bit more temp sensitive then H4350. Then again, H4350 is among the most temp stable rifle powders commonly available.
