Hong Kong is the city that does the most per square kilometre in Asia, which is saying something. In three days you can have afternoon tea at the Peninsula (where the fleet of Rolls-Royces waits outside and the lobby orchestra plays at five), ride the Star Ferry across the harbour with the skyline moving behind you like a film credit, take the tram to the Peak for the view that Hong Kong is built around, spend a morning in the Kowloon street markets, eat two meals that would compete with anything in Tokyo or London, and still have an evening free. The density is not overwhelming — the city is small and the transport is excellent — it is energising.
The Peninsula or the Mandarin Oriental is the hotel question, and it is one of the more interesting hotel comparisons in Asia. The Peninsula is tradition — the oldest great hotel in Hong Kong, in Kowloon, the harbour view from the room, the afternoon tea as an institution. The Mandarin is sophisticated and slightly quieter, on Hong Kong Island, the better address for dining and the one that travels in the same conversation as the Mandarin Oriental Bangkok and Singapore as a category of itself. Three nights is the right amount.