Oscarus

Just one episode, midway through, and the battle is already miles better than Leon vs Diantha. 

The number of different strategies and combinations pulled off from both the sides, could easily tell us about their fighting styles and ways of dueling. While some events were... unfortunate (like Dragonite being bodied by Spiritomb... although it looked almost like Charizard losing to Brandon's Dusclops), the battle as of right now was enjoyable... for the standards of Pokemon Coronation Series Finale. 

And, as I said, this match tells clearly about both competitors: Ash has talent, but Cynthia has experience. 

Ash was able to pull out many various tricks and combinations to fight his opponents despite the odds (like Gengar using Will-o-wisp to minimize the damage of Roserade's Leaf Storm and to burn it, Pikachu cutting Gastrodon's Stone Edge with Iron Tail and attacking the slug with its own attack, or using "Counter Shield" to protect against Spiritomb's Hypnosis), and can quickly adapt to any situation. 

However, Cynthia is far more experienced, which is shown in battle by constantly switching in and out her Pokemon to adjust to the situation and to have the handicap against the opponent. Her Pokemon also have a different types of sets so they might function a different role which suits them the best. She is also seen to be very patient and unleash the ace up her sleeve at the least expected moments - when her Spiritomb's Destiny Bond took out Pikachu - Ash's ace who has taken out 2 Pokemon by himself, and could still fight well. That was a masterful play. 

As of right now, the situation is 4-3 in Cynthia's favor, but out of the 4 remaining, Togekiss has received some damage from Pikachu, and Roserade is burned; while Ash's three next Pokemon are completely healthy. So actually, the chances are equal for both of them - the one who will use given opportunities the best, will win. 

To be honest... I don't really care who wins. As long as they put up a good show, it's fine by me. But with an asterisk saying that if Cynthia wins, she may suffer the same fate as Diantha before, so... Yeah.