Board Thread:Naruto Discussions/@comment-26993711-20170603214204/@comment-734582-20170604125526

QuakingStar wrote: The EMS doesn't give you a power boost so what made him better then his MS self was that he gained perm eyesight and less tech strain which is easily noticeable. Well it's a lot easier to develop proper MS techniques (Like combining eye techniques with Susanoo) if you can use these techniques more than twice per eye. It also helps if you have eyesight left by the time your Susanoo manifests fully (meaning armored).

In both Sasuke's and Itachi's case, they were nearly blind by the time they could really use their Susanoo. Itachi could barely use Tsukuyome and Amaterasu twice, and Sasuke's constant ability spamming robbed him of eyesight in months.