Down vs Synthetic

Technology has come a long way with treated down and new DWR bag fabrics. I'm not concerned about becoming rain soaked, which I can guard against.

I live in the Tropics and typical daytime temps are around 85-90F with 75-95% humidity. The mountains here go up to around 9,000 feet and the temps drop about 5 degrees centigrade per 1,000 meters increase in elevation in high humidity. Typical temps at altitude are around 32F on the low side to the more typical 40 - 60 degrees. BUT the humidity is always high and with weather changes is is possible to have freezing to just below freezing temps.

I am leaning towards a synthetic bag, but hate the weight and size penalty. A Big Agnes System bag would eliminate some of that

What are your sleeping bag choices for high humidity conditions?