Thank you for the explanation.

I do not understand how "Big Stake Holders" are any different than "Big Mining Pools" in your explanation.

Under the above assumption that the risks presented by both are the same, I predict it is less costly for a Big Stake Holder to attack the system rather than a Big Mining Pool.

Mining Pool has Equipment, Operating and Energy Costs throughout time and it's profit comes also from a continuous service, rather than immediate. So it is a long term plan. I argue they stand much more to lose than an equivalent in size stake holder.

I don't see how proof of stake is better security and more decentralization. But then again, I don't feel Bitcoin is centralized when you can fork it anytime you want. It is effectively impossible to control bar physical coercion. Your argument to defend against a centralized Proof of Stake also stands for Proof of Work. Effectively fork it and let them keep their coin.

A Miner with a long term plan has much more incentive to listen to users and less to deviate than a staker with a big stake.

Right now, we are witnessing that. There is an looming threat to change proof of work. We see Miners, Users all threatening forks and let the economy decide. UASF is effectively banking on the fact that users vote with their money. Only Miners stand to lose here. And if it so happens that Miners win, it is because the users decided their coin was better... Not because the Miners imposed that their coin was better.