There are a number of reasons I much prefer Casper over PoW:
In PoW, any coalition of >50% (or 25-33% if selfish mining) can very profitably censor and revert history. In Casper, it takes close to 100% of bonded validators to collude, to censor profitably. Additionally, finalized blocks cannot be reverted by any amount of byzantine behaviour.
Casper is designed to make it as expensive as possible for a supermajority of byzantine nodes to undermine protocol guarantees. Supermajority-of-hashpower attacks on PoW, OTOH, are very profitable.
The ideal is to have a model where consensus is as cheap as possible for everyone, except for adversaries while they are conducting an attack. PoW has to be more expensive for everyone at all times than an adversary might be able to spend at any time. Security-deposit based PoS can make very large efficiency gains, in terms of economic security provided per unit of fees + issuance.
Also, block finality and the concise nature of economic proofs from security deposits makes Casper much more light client friendly than will ever be possible with PoW.
Hope this helps!