If you talk about just singing skill, then Arijit is better then only Bieber. Arijit Singh undoubtedly has magical vocals that can switch between Low voice to High Voice. Arijit has excellent control on his voice especially if you listen to his song he used low notes well that is a great skill if you know too much about signing then you defiantly Appreciate him. He is much more expert in the field of signing, so Sargram and alap is not a big task for him.
On the other hand, if you listen Justin Baber is signing most of his song in flat pitch. That is so much easier for Arijit, and he easily signs a song. On the other hand, if you say Justin to sing an Arijit Singh song then defiantly this is a difficult task for him. And I am sure he failed to do that.
As we already know Arijit and Justin belong to different mother languages and also belongs to different genres, so it is Good compression to compare both of them. Both Singers have excellent voice quality and even have unique singing skills, so compression between these two singers is not a valid compression.
