My experience with inverting subwoofers is you gain more airspace for the enclosure, sealed res goes down a tad (might also affect port tuning a tad as well), cooling is better since its not trapped air within the enclosure cooling the vc with heated air, it's free flowing air that gets sucked in to cool the vc and it's even better if you're driving while the windows are down.
With inverted subs, you'll have to swap the polarity or use the 180 degree phase knob on the amp.
With my temp setup, it's a little louder (to the ear) inverted than mounted in the enclosure. Probably b/c my sub enclosure is a tad on the small side so I gain going to inverted.