Solely by the fact that the electrical consumption is so massive that it becomes practically impossible to support it, ignoring all other factors required, space, labour, etc. It is also not realistic to assume depreciation for ASICs, they would probably be rendered worthless. The difficulty of acquiring (and set up) that many ASICs isn't comparable to that amount of coins.
The shortcoming of PoS is that miners have no need to support any single fork. Since their coins exists across all of the fork, they can support every fork.
In a system using PoW, the wealth gained from mining can be reinvested into future developments. However, this sunk cost is not directly exchangeable with the currency you gain as a reward. Your technological improvements are a byproduct of the upgrade process. Targeted in specific ways, you could try to isolate this to increase development exclusively in non-ASIC hardware but that's discussion for the
other board.
The coin supply may increase in a PoS system, yet your rewards can be restaked directly: a system of compounding interest. So now, you have little reason to store the base currency as opposed to staked currency, though if you ever decided that you wanted to cash out of the network, you could do so by selling to another party. For rational actors, this doesn't change the global staking power: the buyer would stake their currency to generate profit. For a malicious actor to penetrate the network, they need the capital to buy enough staking power and enough willing sellers, or the power to convince enough people to sell.
The security comparison given this context would depend on whether one thought it was harder to generate hash power or to generate capital and influence. (against non-malicious actors)