Is Mangekyō An S rank Jutsu or SS rank Jutsu?

Now, me and Kozai have come to a standoff on this. He says MS and the techniques are more powerful than SS rank jutsu. I think otherwise for numerous reasons. I'd like to hear everyone's suggestions and PROOF from the series and other as to why it is better or it is an S or SS rank jutsu. Now I'm going to wait until I share my argument because I honestly want to see everyone's opinion, partly because Kozai never gave proof of why it's stronger. Thank you again.

2-eye MS S-rank techniques are normally more powerful than SS-ranks.

Case in point: Madara and Itachi

Madara: Could level mountains effortlessly with Susano'o.
Itachi: Forest fire amaterasu.

Both of these are S-rank MS techs (whether 2-eye or not) and were perfectly capable of devastating the landscape, with Madara's susano'o destroying as much if not more terrain as the Rinnegan's Chibaku Tensei. Regardless, for the effort that it's worth in terms of game mechanics (and that fact that the MS counter here is only 100/100), the MS techs are supposed to be that strong.

Madara: EMS Susano'o = Most powerful

Itachi Amaterasu = Strongest because best with Katon


your simply looking at the tech but not the power behind the user which is where your argument is flawed Kozai. Madara could level anything with his susano'o not because it was a Ms tech, but because of the power he had himself. If Susano'o was indeed that powerful then Itachi and Saskue could do the same damn thing..but they can't. As for Amaterasu, Itachi's was so powerful because of his proficency and talent with Katon in general. Once again not because of the eyes but the power of the user. Ms tech's are ranged from A (being Amaterasu in some cases) to SS ( A fully upgraded Susano'o) in which either one could still be dominated or even beaten by a regular SS ranked jutsu. Therefore i am saying that no Ms tech's are not stronger than SS rank technique's.

Well seeing as this stemmed from a dispute over the jutsu that Kou's making.... what's the standardized strength for SS-ranks?