"what are the pro and cons? I am a smaller framed person and do Ok with a stuffed Quetico Pack by GG. Why would one want to make a transittion to this style of pack....very curious about them with all the dialog.....Are there other sources for the barrels locally?"

re-read the hang vs hide threads - the main reason (I think) that people switch to barrels is that they don't feel a need to hang thier food pack, just hide the more or less airtight barrel in the brush near camp.  I haven't really looked at the barrels much, but I don't see that they are bear-proof - a determined bear can get in if he wants to, though a barrel, out of its harness, is a lot harder for a bear to take away than a pack he can just grab by a strap.

Kind of a Canadian thing too, where they tend to do more river tripping than lake tripping - the barrels are waterproof, more or less, and will float better than a pack;  except that after some time, the rubber seals will deteriorate and the barrels can/will leak if they take a ride down the river.   So if you trip with people who use barrels a lot, then you are likely to do the same.