I don't know much about how WebMoney works other than what I just read on Wikipedia, but it looks like WebMoney might be best compared to a permissioned blockchain where a group of companies mine the blocks.
Proof of Stake has the advantages that anyone (with sufficient money, or by gathering into pools) can become a validator, and the system itself provides extremely strong incentives not to cheat by slashing their stakes if they do. This slashing weeds out bad actors over time, as well - once their money's gone, they can't stake anymore.
I could imagine all sorts of shenanigans that could cause a small group of companies operating a money system to cheat, either of their own accord, or forced to by a government, organized crime, hackers, etc. Much harder to attack a huge self-healing group of globally distributed validators with extremely strong incentive not to cheat.
Well I too could imagine some sorts of shenanigans that will mislead the majority of validators especially in PoS that doesn't lock any of validators computation resources. It's even worse in the sense that a validator can be anonymous and doesn't hold any legal responsibility (in contrast with WebMoney). Thousands of validators could be one entity now or in future and you'll never know that (in contrast with PoW). Some infuencer (just like Vitalik) can come and convince validators to mine incompatible fork of Ethereum - you can do this for free and won't be slashed on main chain - and why not, maybe this fork will prove better and people switch (yeah this can happen with any crypto that's not Bitcoin)?
All I'm saying that Satoshi really produced the one undeniable cryptocurrency. His idea is sound, you don't need any friends or websites, or "common" knowledge besides his simple idea of the most work burned chain. Anything other is really questionable.
Proof of Stake has the advantages that anyone (with sufficient money, or by gathering into pools) can become a validator, and the system itself provides extremely strong incentives not to cheat by slashing their stakes if they do. This slashing weeds out bad actors over time, as well - once their money's gone, they can't stake anymore.
I could imagine all sorts of shenanigans that could cause a small group of companies operating a money system to cheat, either of their own accord, or forced to by a government, organized crime, hackers, etc. Much harder to attack a huge self-healing group of globally distributed validators with extremely strong incentive not to cheat.