Being dragged is one of my worst fears about falling from a horse. I ride in a half-breed saddle which has ox-bows so my feet naturally just slide right out of them when I come off.
Saddlebronc riders use oxbows because you can really shove your feet all the way home and they stay. I wont ride in them, or the deep roper stirrups that you can shove your upper thigh through, because I want to be able to kick out if need be.
And be careful with what your oxbows are made of, because they are thinner the material makes a difference if you have a horse fall down on his side, bends and squashes your stirrup to where you can't get your foot out.