I don't have a local dealer, so I can't see either of these in the flesh, and the pictures on the internet aren't that great. The B-Bag seems to be pretty heavy, and I don't think I'll need the wheels, plus the AVC bag is cheaper. But how good is it? How easy are either of them to carry on the bike (S6L with S-Bag, M6R with Touring Pannier)? I intend to ride away from the bus station.

Hmm, I seem to have talked myself into the AVC bag, but some feedback would still be nice.

I have the B-Bag, and it's a really nice bag for transporting a Brompton, but that's mainly to a hotel where you will leave the bag there. It's well made and beefy, but that's the problem: it's heavy. And while it folds, is doesn't fold very small. You can lash it folded to the rear rack, but it sticks out a lot. I tried to lash it to my backpack, but it's pretty heavy and bulky. Simply put, it's great for transporting a Brompton but you wouldn't want to take it with you somewhere, either on the bike or on your person. And it is expensive. I got mine free since the bike shop screwed up on the color of the Brompton I ordered, so it was cheaper for them to give me a free B-Bag than take the bike back.