As far as fly fishing, I think the Cabelas / Bass Pro comparison would change each time by looking at different locations.
On my way to Montana, I made it a point to stop in Sydney, NE and do some shopping at the Cabela's store there. Since Sydney, NE is where Cabelas has their headquarters, I reasoned it should offer a wide selection of everything. Boy, was I disappointed. I've been to other big Cabelas locations and the selection was far superior. Sometimes it's tough to make that comparison.