Are dual capstans always better than one?

Hello everyone,i just bought a mint Teac V-900X auto calibrating 3 head direct drive cassette deck (circa 1985) and to my amazement it only has one capstan,i would have thought that such a high end deck would have dual capstans..The sound and build quality of this deck is AWESOME.So is just that companys like Teac can do things with one capstan that it takes other companys two to do?Thanks,Keith H.