Which one is better for phd in engineering ? NUS or UNSW ?

Can you explain what the acronyms are? I have no clue.

NUS = National University of Singapore and UNSW = University of New South Wales. Sorry for the inconvenience. I should clarify those abbreviations in my post.

Hi. I think in terms of ranking they are both top world with National University of Singapore is rankied 11 in topuniversities and University of New South Wales ranked 45.
The big question is where do you want to study? in which country? I think Singapore and Australia are totally different.
Also do you intend to stay in the same country of your PhD after finishing? How is the job market in your prospective field? How easy to get a work permit in each one (assuming you are not a citizen of the two contries). In my opinion, research wise, both are sufficiently top. The country is the real choice.

I am with eng77, the country/culture is far bigger than the university ranking. You want to work in environmental that will get the best out of yourself. Because at the end of your PhD people will judge you on your publication record more than which university you went to.