I wouldn't say those are equivalent. Any exploit in v8 gets full access to the process, which in a multi tenant situation means access to other tenants. And v8

I wouldn't say those are equivalent. Any exploit in v8 gets full access to the process, which in a multi tenant situation means access to other tenants. And v8 itself is hardly bug free. Reducing the JS API surface might reduce the probability of finding a way out, but it doesn't reduce the blast radius. 2008 was also 14 years ago, I'm not sure that's the right bar for security! The OP was also speaking to using v8 getting you the same level of security as Chrome, not to architectural decisions in CF beyond that.