I think we are saying the same thing. I'll put it a different way...
H110 doesn't safely make light or medium loads. H110 is a full bore powder that makes terrific max loads. It's the best way for a reloader to get full velocity while staying safely within SAAMI limits for the cartridges that it is designed for, and .44 Mag is probably the most popular chambering for H110 used everywhere in North America.
You may have a "start" load listed in your published guides, and it is a safe load, but it's still a very warm load. If you believe your S&W doesn't handle 300gr bullets well when they are loaded warm to hot, then you need to pick a different powder.
You say the bottom loads are listed as one grain under the top load. NO WAY that's going to be a light load. It'll be safe-- YES! But it won't be light. If you don't want to subject your S&W to a heavy load, then pick a different powder.