Buying either tune to save money on fuel is a poor argument.
Check out Carmax's savings calculator. Let's say you get 5mpg improvement, which is quite generous, which bumps you up from say 32mpg to 37mpg, over 15k miles a year, that's only saving about $250 a year, BEST case scenario.
http://www.carmax.com/enus/mpg-savin...r/default.html
People get these tunes for the added power, not fuel economy. Power comes at a price, fuel.