I say it depends on the mods and driving style. I've upgraded my 2.3L Quad, and know for fact I'd take a stock 3.8L N/A (Bonnie, GP etc.) Both in gas mileage (regardless of how I drive) and speed (I've done it more than once). I average 29 mpg with combined city highway and "rigorous" driving too and can easily out accelerate 3.8's 3.5's, 3.4's, 3.1's. A supercharged 3.8 is faster, but not by a ton. I don't generally go looking for races or anything, but the extra power is enjoyable in daily driving. Also, I'd much prefer the smoothness of a V6 to what I have, but the gas mileage is nice also. I plan to wear this car out, then move to somethng bigger and more expensive no doubt.
I'm not disagreeing wholly, but adding that it certainly depends on many factors. For example, my intake only causes more power and more consumption if I request it with my right foot.