Hello Aspirant. I hope you are doing great. Both of them are really very good.I'll tell you cons and prons of them. And then you can make up your mind from whom to study.

Physics wallah - His youtube videos are really informative and easy to understand. He starts from basics and then reach to next level. So a student who wants to learn from basics can watch him but the videos are little too lengthy. Takes a lot of time and patience.

Talking about unacademy , lectures are small, crisp and to the point. It's a good platform too for jee preparation. You can practice questions and learn concepts. It's less time consuming.

Hope I Cleared your query.