Speed,and energy is greater with the 150gr loads

This will always be true, but not always needed. Accuracy will almost certainly be less, with 150gr powder/pellet load.

Most shots will be less than 100yds

...at which distance, 90-100gr powder and a 300gr XTP will kill deer quite dead

I was under the impression that the .45 cal was the hot ticket for long range

I've heard the same thing, but I have heard much grumbling about probs with .45.... and I don't think they offer any substantial advantage over a .50

I think the 80/20 rule applies for muzzleloading, or maybe the 95/05 rule: you can put a lot of extra effort/$ into getting a few extra yards & better paper ballistics, which in the real world of the deer woods are almost never is required, and rarely pay off. But then, I've never killed a deer past about 90 yards - often can't see much further than that - and at that distance a pedestrian XTP on top of 90-100gr of BP/BP substitute is quite deadly.