Gotta agree with the guys here, bio media is bio media. But surface area, now that is something different. More surface area means more bacteria. Also, what are you willing to spend?
At one end, you've got Eheim's Ehfisubstrat Pro with 18,300 sq. ft. per 1 US gallon. I really like this because I inherited a lot of it for free but most importantly it reminds me of Cocoa Puffs.
Then clear across the other end of the spectrum you have $5 per pound pumice (cinder stone) which has about 16 sq. ft. per gallon.
Here's a handy table comparing various medias. Pay no attention to the activated carbon!
"You are much better off with no numbers than meaningless ones. The minute you believe numbers uncritically, that is, without understanding how they're calculated and how well they measure whatever they're supposed to measure, you will generate a breed of employee who will produce numbers and not results. Your data-processing system will then serve not to describe reality but to lie about it."
-Micheal S. Montalbano