Hi Pete, Welcome to the forum.
I'm sure someone will come along here and give you a good answer, but it seems it would depend on what gun you are going to be shooting this in.
IMO pellets are for in-lines, and loose powder is for caplocks with a somewhat limited use in flinters.
As far as a honest comparison of the two I don't know how you would do that as they appear to have different applications all together.
I bought my first can ever of loose T7 this year, and was pleased with it's performance in two of my cap locks, although I still prefer real black powder.
If you are shooting an inline, I suspect the pill to be the thing you may be interested in. Seems to be the thing in vogue today, although fine tuning a load has the appearance of being problematic due to the limited weights available in pellets...just guessing, as I don't know for sure.
Welcome to the forum. :thumbsup:
Russ