My understanding is that PoS has attack vectors that are not present in PoW, giving the attacker a cheaper way to totally control/destroy the network.
Can you elaborate? I have observed exchange price action and noticed that when 1% of NXT is purchased at market price, this drives the price up 25%. If that is extrapolated to 51%, the funding would have to be in billions of USD, not to mention there is no single place where that amount of coins can be purchased. At the same time there are calculations that buying up hardware to control 51% of Bitcoin hashrate only requires $500 mln.