Naruto and Sasuke are much stronger than Indra and Ashura,
--They both recieved power directly from Hagoromo, and recieved ALL of Yin and Yang half respectively,, indra and ashura on the other hand only inherited it, meaning that their yin and yang were not only less in quantity, but the quality itself would be inferior to naruto and sasuke due to the latters recieving it from the man himself,
--nothing suggests that ashura had all the bijuus under his command, and nothing suggests that he had absorbed a heck load of nature energy, the only thing thats the same is the avatar itself, however narutos avatar is not only larger but its far more amplified due to him having a much stronger senjutsu boost,
--indra on the other hand didnt even have a Rinnegan, he had something like an EMS, or a devolved rinnegan, and his full power was still most likely PS or Indras arrow, Sasuke on the other hand has his PS as a vessel for the bijuu, meaning that its firepower and quality of chakra is much higher therefore yielding a much stronger susanoo, and just because his strongest technique is named indras arrow, doesnt imply in any way whatsoever that the scale of their jutsu is the same,