Board Thread:Theories and Speculation/@comment-30631705-20161130044038/@comment-734582-20161130090024

it seems that when a user obtains a double MS, one sharingan will feature an  offense power and one a utility power.

Amaterasu is equivalent, not inferior or superior to Kagutsuchi. Kagutsuchi doesn't offer the option of projecting the fire over large distances, it simply grants control.

Obito's Kamui is the same: it grants greater space-time control but doesn't allow long-distance projection of the power.

The drawback is obvious: having both powers grants more control but having different powers grants more options.