Macao isn't the same party/club scene that Vegas is. If you went that direction, I'd probably make it a Hong Kong trip with Macao as a side venture from there. I mean, unless you guys are just huge gamblers and looking for that as the primary focus of the trip.

We actually spent Dec 31, 1999 on the Vegas strip. Booked our hotel room at noon that day for around $150 at Treasure Island. Of course, TI isn't top-shelf Vegas, but it wasn't bad and was actually closer to the Strip "center of gravity" in 1999. It was a fun scene...glad we did it once...but no real desire to do it again.

What's your starting point for this trip? Those aren't the only two good NYE scenes in the entire world...

Two things you probably don't have to worry about are severe weather and English speakers. The weather will be adequate in both places and you'll find enough English spoken in Macau for it not to be an issue. (Plenty of English is spoken in HK, of course...)