Hong Kong operates under a different legal, immigration, and administrative framework from mainland China under the "One Country, Two Systems" arrangement. For expatriates, this means a fundamentally different experience: English is an official language, the common law system applies, and international banking, healthcare, and professional services operate to international standards without the friction points of mainland China.
The trade-off is cost. Hong Kong is one of the most expensive cities in the world for housing. A studio apartment in a central district costs what a spacious family flat costs in Chengdu. School fees at international schools are substantial. Everything is expensive except the outdoor environment — the hiking trails, country parks, and island-hopping opportunities that make Hong Kong's natural setting among the most dramatic of any major world city.