I've read and been told that riding clipless is more efficient, but had no idea how, other than it keeps your feet (for the most part) from flying off the peddles at unwanted times. Is that how? They allow you to "pull" better?

My platforms have little (plastic) spikes which work well with most running shoes by digging into the tread, not necessarily as some of the metal platforms I've seen which make my shins hurt just by looking at them.