The Pyramidion is not 'easy' to pilot, but, in my opinion, is the easiest to crew and maintain. Only one engineer is needed to keep the hull and engines running, and they're so close together, it's not a terribly hard job. The other two crew members both just focus on gunning; one of them having to keep the balloon in check. The gunners don't have to account for ship movement to throw off their shots since the guns are on the front.
The Pyra is the only ship where one engineer can repair all three engines in less than three seconds (minus the Galleon when you jump on the ledge). Low levels can better operate on a Pyramidion instead of, say, a Squid or Mobula.
Easy to gun, easy to repair, easy to stay on target, very fast, high armor and hull, small balloon, ramming ability... The Pyramidion really only has one weakness, and that's it's turning and vertical movement which can be overcome with pilot tools.
TL;DR: Pyramidion is the easiest ship.