I’m well aware that it’s intended as a replacement for PoW, but I’m pointing out that they have very different security guarantees. For example: imagine there'

I’m well aware that it’s intended as a replacement for PoW, but I’m pointing out that they have very different security guarantees. For example: imagine there's a vulnerability in the reference client. With PoS, a payload can compromise nodes and replace their chain with another (valid) chain, leaving everyone wondering which chain is the right one. With PoW, no attacker can alter the chain without invalidating its proof-of-work.