The higher voltage will certainly be the better option for metal halides.
Also put the circuit at least over two or more section fuses, mcb's in case of a cable fault, so at least you can keep half or part of the lights going.
Now these days when streetlights or parking lights are not working, people and councils make a big issue about it because of safety, tagging, unlawfull damage etc.
If you use incandescent lights usually a lower voltage (110 or 24) is better because filament lamps tend to have thicker filaments and last longer. ( for streetlights this is rarely used now these days ).
