Hong Kong is "Sub-tropical". I have tried the Mono panels and the poly side by side on the bow of the yacht. I compared them this way... Two 300w 36v panels each in parallel (2 mono and 2 poly). Two mono to a morningstar MPPT, and two poly to another morningstar MPPT.
Between the hours of 11:00 AM and 2:00 PM the panes both seemed to be very close. There were times that when a cloud would pass the Mono would still be producing a bit more then the Poly... but at the end of the day, both sets under the same sun. It was an even match for the amp production into my battery bank.
Poly is a bit lower in price per watt for Grade A panels, and being on the water. The blue of the polly looks good on the bow of the vessel... HaHaHa
One other thing. The panels on the yachts are flat, and in the winter months the Poly was still giving good power.
I guess it is mainly a personal choice now. They do work very well, and the factory as assured the frames to be for marine salt water applications. That is a benefit in itself for me ! I tested the 150W Poly 18v panels with these frames for over a year, and they are the same as they were out of the box. Salt and Aluminium do not play well together !
$0.47 USD per watt (Grade A Certified) including door to door delivery is also a factor that my wallet is happy with !