That's if he's actually capable of flight. You mentioned earlier that you thought he was. Even so, Ness is capable of midair dodges (like all SSBM characters) that make him immune to damage for a second or two. Plus, Ness has abilities to block damn near anything Cloud throws at him. If Ness needs to get away to regroup, he can use Teleport to get himself away from Cloud quickly. If he needs defense from physical damage, he uses PK Shield and it cuts the damage in half and relects some of it back at Cloud. He's just more versatile.