I believe PoS is bad because you can rewrite the chain without redoing the work.
Meaming that if 51% doesn't like something they can go back and rewrite 24H in a few seconds. Hence sending 1000ETH to B instead of A.
With PoW you have to re-mine the blocks which means this is practically impossible as the original chain is progressing too.
You can try to avoid rolling back too many blocks, but that is an artificial and only locally enforcable rule. As far as I know there is no such rule today on ETH.
Honestly speaking, I just think that each algorithm has something special to it and some problems as well. You just have to find which one works best for you and how you can make the most out of each one.