whichever is cheaper.
Environmental Law isn’t really a thing, just a couple of electives/clinics offered at US law schools. Check out each school’s curriculum for an LLM and see which would allow you to take more Enviro classes.
As far as international Rep, it probably depends on whether Europe or Asia. GULC is probably marginally higher in Europe and UCLA in Asia. But again, Enviro Law is really not a thing so there is no reputable ranking per se of that speciality.