I haven't tried clipless, but I find toe clips to be a huge advantage over platforms.

(unlike some people who assert that toe clips don't do much, I find that 1) they keep my feet on the pedals, so I can spin/sprint faster 2) they really help on big hills, where every ounce of energy counts and 3) they really help on long stretches, to alternate the muscles you use)

However, I can't think of a way of rigging regular shoes to use on a clipless system that probably wouldn't reduce the efficiency of clipless to that of toe clips/straps. Go with toe clips.