Ethereum is almost definitely a security. It had an unfair issuance and is controlled and influenced by a small group. I mean it has a roadmap by vitalik!
Unlike proof of work bitcoin, the control authority of the entity that is the Ethereum network is now entirely in the hands of the top stake owners, just like control authority of a company is entirely in the hands of top shareholders.
At the end of the day, the specs are defined by the community and implemented by the 10 independent client teams, compared to 1 with Bitcoin.
Besides, node operators still have the choice to update or not update their nodes, similar to Bitcoin.
Ethereum is not a security
There is not much difference between a traditional tech company and Ethereum.
Meanwhile Bitcoin has been code complete since the whitepaper was released. There is no roadmap.
Ethereum is a security, Bitcoin is a commodity.