tailingloop, keep in mind that I am Orvis so I am refering to the Mid Arbor and the Large Arbor.
The LA will retrieve line faster (refering to the line picked up per turn) than the Mid Arbor right down to the backing. You do however lack in the backing end on the LA as to the MA.
I do agree on what you are saying the difference is however.
I bought a BBS V for my eight weight and put a grundle of backing on it so the line does come off an pick up quicker, plus I have all that backing to wave to the fish as it strips it away before I loose every thing LOL. The BBS was my choice cause of the weight. It is such a light reel that even with all that backing and line it balances out that 10' 8wt. nicely.
Be sure the reel balances out your rod.