If you drive on smooth highways, there should be no difference, but on the bumpy road or dirt road I can tell right away the tire pressure is high, ride is harsher. The theory is that lower tire pressure would make larger contact with road surface, providing better grip, with high tire pressure smaller footprint is achieved with most of the car's weight in the center of tire, but that's only theory, if you get better grip , higher MPG and the same comfort with overinflated tires, more power to you. Just keep in mind, every time you take car to the dealer and if they do check tire pressure, most likely they will lower it, so you'll need to pump it up. Also you loose something like 1 PSI for every 10 degrees of temperature drop and my tires slowly leak out the air, something around 1-2 PSI every 3 months or so, I heard aluminium is porous and it will let air go very slowly.