Oh, and if you want to use something other than the movie than there's this...
G-canon is absolute canon; the movies (their most recent release), the scripts, the novelizations of the movies, the radio plays, and any statements by George Lucas himself. G-canon overrides the lower levels of canon when there is a contradiction. Within G-canon, many fans follow an unofficial progression of canonicity where the movies are the highest canon, followed by the scripts, the novelizations, and then the radio plays.
ROTS script...
YODA: (continuing) If so powerful you are, why leave??
YODA ignites his lightsaber.
DARTH SlDIOUS: You will not stop me. Darth Vader will become more powerful than either of us.
DARTH SIDIOUS ignites his lightsaber.
YODA: Faith in your new apprentice, misplaced may be, as is your faith in the dark side of the Force.
Their swords CLASH. The battle is extremely fast and furious.
201 INT. CORUSCANT-SENATE CHAMBER-MAIN ARENA-NIGHT
PALPATINE seeks refuge in the vast Senate Chamber. He gets into the Chancellor's Podium and it starts to rise up into the Arena. YODA makes a giant leap into the control pod. The sword fighting is intense in the confined space.
203 INT. CORUSCANT-SENATE CHAMRER-MAIN ARENA-NIGHT
YODA unleashes a ferocious assault on PALPATINE, causing him to almost go over the edge. The Dark Lord drops his lightsaber but recovers with a BLAST OF ENERGY from his hands that surrounds YODA. YODA is deflecting the Sith Lord's lightning bolts.
So yeah, Yoda > Sidious in sabers.