Yet in A New Hope, both were locked in battle poses and very much like fencing strokes in the Death Star. Any explanation? Age is not counted hor... look at how old Yoda was in Attack, yet he can bounce around, would suggest Jedi's have superior stamina and vigor over mere mortals.
My take is Vader's body is mostly mechanical, and hence, can't move as much as when he did as Anakin. Also, what we couldn't see, both Vader and Obiwan were locked in a battle on the force level and both were equally strong in the force that negated any advantage one might have over the other.
