"Maybe you should read he manga to see all that happened since then?"

That's the rude part. You're not attacking the argument, you're attacking the person that made the argument, hence, rude, arrogant, uneducated, and meaningless.

But your first paragraph made more sense than your second. Ok let's break your argument down so we can discuss it better.

Higher stats - sure ok can't beat that. But that was so long ago too, mind finding evidence about the current stats of Shin and Mouten?

Better showings against atronger opponents - there has not been a previous battle where Mouten was given a chance to "show" against powerful enrmies. It's because he doesn't care about defeating commanders. He cares about winning the war. Examples: The guy who has the Bakuya sword gave Tou a problem going against hin toe-to-toe, but Mouten decides to ignore him instead and focus on something else. Also, he got injured by Kanmei, hence no other chance for a showing. You think Shin could've stopped Kanmei's blow if he were in the same spot? Maybe. Maybe not. We don't know, so I wouldn't make that as my example.

It's more oppotunity and privilage that Shin was able to be in the cebter of most storms because HE IS THE MAIN CHARACTER, obviously (and for good reason too). But I just think give Mouten's technique of finesse, intelligence in analyzing combat situations whether individually or over a battlefield, overall I'd like to speculate that Mouten is better, even perhaps martially, against Shin.

We'll see in the bext few chapters I guess. Mouten hasn't been mouthing off dumbly as Shin has been doing for the longest time before this battle, and easily saw though Ousen's tactics for the current battle, so I think there's A LOT we don't know about Mouten (being a side character) that we're (you in particular) may be underestimating.

THAT'S HOW YOU DEAL WITH AN ARGUMENT. ;)