The big, fat, double-decker Megabuses will soon get to pick up riders right outside the Port Authority Bus Terminal. (They can’t fit inside.) But they won’t have to pay the $10 million fee like their rivals within, including Greyhound and Peter Pan, since curbside pickups can’t be regulated by the city. “We ask for a level ground to compete rather than having the city show preference to one business over another,” competitors wrote in a recent letter to Mayor Bloomberg. But he should probably have to ride with a stuffy, smelly, crowded discount bus service before making any decisions.