I guess I don't see one method as being inherently better than the other, I think they both work well, it's more a matter of what are you trying to accomplish?
Mine is gravity fed with a dedicated drain from the tank (not a T off the main drain to the sump). Yes I have a re-circulation pump that feeds air into the skimmer but I don't need a feed pump or a port off my sump pump manifold. I also wanted to get more flow from the 180g DT to the sump, so an extra drain from the DT to feed my skimmer does the job perfectly.
As for the gravity system being hard to adjust or tune... I suppose it may depend some on what skimmer you use. I have an Aqua Medic 5000 Shorty and the feed from the DT has a ball valve for control. It works fine and is pretty easy to tune. I will switch out the ball valve for a gate valve some day, but I'm in no rush as it works great the way it is.