The argument above assumes that it is simple to acquire and manage the resources needed to attack the network. As we know from sufficiently secure coins, this is impossible. 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.
I think there's two sides to it: 1) how difficult is it from a monetary perspective and 2) how difficult it is from a practical/implementation perspective.
Whilst I agree that it's difficult to acquire and manage the resources to attack the network (and therefore much more difficult form a practical/implementation perspective), I'm not so sure that the combined cost (monetary value) would exceed 51% of the supply of coins (which is what it would take under PoS).
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)
Yeah I don't think the security comparison is clear cut which is the more secure.