Most other learning platforms will present you the flash cards in the order that they became due for review. With SoYouLearn premium you will first review the most important flash cards, i.e. the flash cards that are due for review most urgently.
Consider the following scenario: It's Friday evening and you want to review your flash cards. You only have 10 minutes but in your review queue are over 300 flash cards due. With the premium subscription you will review the most important flash cards first and can then leave the other (less important) ones for another day.