I would say that POS requires a centralized authority to prevent collapse.
That is a statement, not an argument.
Who is this authority?
In both open source versions of PoS and PoW the authority is split between miners or stakeholders/ users or nodes / and developers.
The difference is within PoW the target is always moving and is wasteful (both a valid criticism and a strength) so the power structures are always shifting based upon technological development and business advantages. This has been proven by changes in not just with mining pools but asic manufacturers, and miners themselves over time. Miners are forced to distribute most their coins to cover business and electrical costs.
With PoS the largest shareholders are fixed targets who are less likely to be unseated due to not being dependent upon constantly reinventing their business model and technology to be competitive. Stakeholders can choose to horde or sell off their coins from forging/stake holding thus ensuring some early adopters remain in positions of authority.
Rather than discussing changing Bitcoin over to PoS, I think we should merely add a TaPoS layer or sidechain to PoW to further strengthen Bitcoin's security and allow for quicker confirmations. The environmental concerns will eventually be addressed anyways by the exponentially decreasing block reward and market forces.
Another thing that I like about PoW that is rarely discussed is that it is a technological arms race that spurs ASIC development and cooling technologies.