I have to say, Palpatine's duel was ridiculously botched and condensed. You take a Jedi who could stand toe-to-toe with the likes of Obi-Wan and Anakin, and then have him get owned like a fish out of water by some old goon, and I officially declare you queer. ''You'' being Nick Gillard, who needs to be put down.
He was fighting both Mace and Kit during those 5 seconds. Vader doesn't even have to do anything until Kit dies.
EDIT: Hm, Kit did have space after Kolar and Tiin were dispatched. He had more than a few meters to his left yet he just died
Anyways, wasn't Palpatine faking with the lightning? Mace could beat him in a pure saber fight, but his force powers are insane.
Not entirely useless. It's hard what to make of it, but I think it was issued so that fans know Vader was getting kinda close to Sidious by ROTJ.
But Palpatine was more powerful. One of the earlier theories was that Vader was always more powerful than Palpatine, but Palpatine had a "mental" domination upon him. This was of course, disproved by GL's comments.