Sure a Power Belt will take a thin skinned deer broadside at medium distance and do a decent job if you don't over load it.
For me that's not the problem, I live in the hills of AR, if opportunity knocks a 400 pound wild boar that has a heavy shield over his ribs and likely an angled shot on top of it or a nice big black bear with heavy fur and a tough hide. I have been charged before and I want some thing I can depend on for a certain amount of penetration if I am forced to take a head on shot. I use Gold Dots and SW and I used to use XTP [and still have several hundred in my bullet cabinet] I think that a person has to take all the possibilities into consideration when they chose what bullet to carry in a muzzle loader. How would you like to have an animal some body else wounded charge at you and have a Power Belt with 75 gr up the spout? Lee