I give it to Ash.
Saber has precog, but in 6 vs 1 match, she still has hard time to deal with them. Not to mention that all of them is around 7-A especially Pikachu and Greninja who far superior to normal mountain level rank.
Saber's magic resistance can protect her from some moves. But since Ash's team have members that on casual mountain level. Plus they also have several physical attacks(Iron Tail, Flying Press, Aerial Ace, Brave Bird, etc.), so I don't think magic resistance should be a problem.
If Ash lucky, he can also use Pikachu to paralyze her. And he can increase success rate when combine with Goodra's Rain Dance.
For Saber best attack, Excalibur. She can charge it really fast if she want. And can also blasts her opponents with the Hammer of the Wind King before charging. But since this is 6 vs 1, I doubt really hard she can stop them all before success using it.
Even Saber succes to use Excaliblast, I think most of Ash's team can dodge. Noivern, Talonflame and Hawlucha can flight, left of them can also ride on first set to dodge. Not to mention Ash also has a way to call them back to pokeballs for dodge it.
With this, I think Ash got thid hihg-diff.