PoS is way more convenient for its userbase, therefore has got a higher chance of adoption

51% attack is meaningless:

A PoS coin is protected against a 51% attack because it is practically impossible for someone to gather enough coins

Not enough coins for sale. One would have to gather at least million of coins.
Trying to buy that much coins would push the price to extreme highs.
But once a currency has enough market cap, it becomes extremely unlikely or even impossible to gather enough coins

PoS is an interesting solution for privacy

Staking interest anonymously on anonymous deposits, like Spectrecoin just did (on trustless setup unlike PIVX which)