14 feet does sound small to me. I'm rethinking that and wondering if I go with a slider, why not just make it the full length of the steel and go 20 feet? The weight is going to be considerable, but if it's on concrete and a track, weight wont matter. If I go with a swing, then that's just too much weight. Double gates really don't appeal to me.
As mentioned, I can see where a sliding gate might be more secure. In a big storm, or strong wind, or just somebody trying to push the gate open, I think a swing gate would be easier to move then a slider when in the closed position.
I've been looking at tracks and wheels.