two legendary martial arts masters meet for the first time
vs Oogway (just saying...)
So we're going with the most recent Splinter? We see him toss Letherhead, who is many times his size, across a room like he's made of cardboard.
Splinter for the win
Splinter. Miyagi hat never been in a real life or death situation, while SPlinter had always to face enemies like Shredder.
I'd say Splinter, just because I think he trained the Turtles a little better than Miyagi did his disciple.