While Cardano has over 670 active staking pools, now that looks decentralized and more secure. 
And less than 1% of the Cardano users, hold over 50% of the coins. Yeah, you don't have centralized problems, but you have another pimp above your head; your wealth distribution sucks. With PoW, you are at the mercy of the top 4 pool operating overlords, which is ok, if you like being a slave to whims of those 4 people.
With PoW, you're at the mercy of the pool that incentivizes you the most. There are not only 4, just like there are many pools in PoS.