He is asking about the B Model and the Pro Model, neither of which are even close to an A Model. The deck is 2 inches shorter and half an inch lower to the ground. It is a completely different ride that he probably doesn't want to ride if he wasn't asking about it. And his question was not Pro VS. B it was "is it worth it to reinforce old b's?"
The answer is YES. I have been riding the same B for almost 2 years now and have yet to switch over to Pro Models even though I have one. The Pro model might be a little stronger but if you have a B Model or can find them cheap they are worth buying and reinforcing.