I live in NZ, but work with mostly US SaaS'es. Got 1 gpbs fiber but I'm torn between downgrading to something like 500mbps which also downgrades your upload and upgrading to 6gbps so I get better international speeds (right now it's something like 100mbps tops).

Yup. For those interested we have a similar approach where the fibre to the home is owned by a regulated provider that is required to offer its service to all retail service providers (RSPs) at the same price. Competition is strong.