If you tried your brother's Imperial and liked the feel, I say go with that. At least you will be getting something you know fits you well. Conversely if you went for the B-17 Narrow and didn't like the feel as much you would always regret it. You had a great opportunity to try one of these saddles thanks to your bro - you know it fits and you already know you want a brooks - I think the decision is pretty clear.