The pellets seem to work ok out of my inline. I shoot (2) pellets behind a 250 Shockwave from my T/C Omega X7 without issue. I was shooting woodchucks fairly consistently at 180 or so yards over the summer. Fairly expensive to use for woodchucks, but a lot of fun nonetheless. Anyhow, life's too short to put a price on fun. I never tried the loose powder.
With the Wal Mart clearances I have paid as little as $9 a lb to $17 a lb. I thought that was pretty good. As far as corrosive, I'm sure there is some science out there but for me it actually seemed better but I do not leave my gun sit dirty more than a day or 2. Even then I swab out and wife off exterior surfaces with TC 13 and then lube until it can be given a good thorough cleaning.
It all in what ya like and how you do it.
I would say the biggest advantage is the cleaning. No smell, no oily black gunk, no hot water. no dishwashing soap etc. Just a stack of wet and dry patches in the living room warm and toasty watchin the game!!