Depends, but Magnepan seems to have the best. The Decca ribbons failed a lot, unfortunately, but maybe they have improved them.
I BELIEVE (don't shoot me if I am wrong, it has been a long time) that the idea is to move as little mass as possible.
Evidently, along with the best (most accurate) speakers on the market, Magnepan has come up with a ribbon-style that is hearty and accurate. Not bad!
Cheers!