Where's your rebuttal? I don't see anything disputing the fact that PoS is much more expensive to attack against. You just keep saying Bitcoin is expensive to attack, that's your opinion, I don't believe $500m is expensive for a well funded and determined attacker, such as nation government or big banks.
How many zero-day vulnerabilities and network nodes do you think you can find with $500 million?
With PoW nodes, they have no reason to be storing a "hot wallet". With PoS nodes, every node has a "hot wallet" in order to prove "stake".
The implication is that a determined attacker may be able to control more than 50% of the "stake" for a lot less than $500Million. As a bonus, they would be using less than 1MW of power while attacking the network (assuming thousands of machines to get good connectivity/node isolation).
Yes, I will only accept bitcoins with 12 * 6 = 72 confirmation (12 hour ... "old" money) so DOUBLE SPEND will NOT be possible with only 90% of hash power.
With >51% of the hash-power, an attacker
can roll back transactions. With 90% of the hash-power, they can roll back 8 hours every hour (in secret until they release their fork).