Don't know about studies. I do know I've seen a difference of 5 to 10 grains of pyrodex make a difference in accuracy that I could tell without using a ruler. Last fall I saw a difference I would not have believed. Fifty yards, factory iron sights, 1962 vintage original equipment eyeballs. First group, pictured right, 85 grains Pyrodex RS, by volume. Second group, slight adjustment to the left, and reduced to 80 grains RS.
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Your results may vary. If you're happy with pellets, that's great. Even if they were legal in my state, I would NEVER use them. Easier to use? Easier to just eat Spaghetti-O's, but it's not that hard to boil water to make pasta. It's cold outside? Got a couple extra pre-measured charges in spiffy little plastic containers. Pop the top and poor them down the barrel, pretty much the same as you would with a pellet, I think. No, I see no advantage to pellets. Just a potential horrible limitation.