I only have a vague idea of proof of stake, but I think I reasonably understand proof of work. In the case of bitcoin, the whole hash thing business has to be combined with a mechanism to increase the difficulty according a certain time calculation. Now this difficulty/time calculation is merely a matter of good faith, and hope that a majority abides by it. If you look a bit deeper, the whole hash function itself relies on good faith, also called the 51% risk/attack whatever.
And hence you have currencies like ripple, which are just faith (maybe one degree higher compared to bitcoin and ethereum) as far as I can see, without any hash or other garnishing. This does seem to be equally functional. So did Satoshi over-design bitcoin? Does this suggest that a whole new generation of minimalistic cryptos will completely sweep away bitcoin, ethereum and the likes?