The difference between the two is the way the frames are held
in a radial extractor the frames fit in like spokes in a wheel.
in a tangential the frames fit like the rim of a wheel
in a radial extractor you do not reverse the frames to extract
in a tangential you reverse the frames to extract the opposite side
you can reverse the direction of rotation on most radial extractors, while not necessary, it will dry the frames better, that is you get a little more
honey. To me radial is the only way to go, but they do cost a bit more
and are usually larger.