Satoshi was long term thinking but here it's more based on the circumstances. POS can't bootstrap itself, it's always based directly or indirectly on a POW bootstrapping
Proof of Work is ideal for what satoshi wanted because together with the blockchain it provides probabilistic agreement with anonymous participants and the reward for participating is bitcoins.
Most forms of consensus would work for a public ledger where ECDSA is used to prove ownership of whatever is written in there.
The functionality of the blockchain can easily be covered by a bunch of distributed servers reaching agreement (i.e more or less what ripple does) however you need trust in such a setup. Trust requirements are extremely lessened in a PoW system. (no miner owns a majority, large numbers of miners stop mining at once etc.)
PoS is less anonymous than PoW because you have to reveal your stake so the coins minted are tied to you. Of course you can augment this situation with some form of coin mixing or zero knowledge proof but thats beyond what I want to say. For PoS it is harder to find a way of distributing coins. PoW provides rewards for participating and those are then spread. PoS requires initial coins to generate rewards.
You could implement some form of lottery in a PoS system to initially try and spread coins to make it more fair.