I think the Olympics have more of a chance at growing the game in a place with some hockey infrastructure and a semi-reasonable competitive team. A place like Germany, France or even Japan fits the bill. For instance, having Leon Draisatl and Grubauer starring for Germany and having them pull off an upset or two could really generate some interest in that country. They have some infrastructure already with a decent professional league, rinks, hosted the WHC, people who aren't too averse to skating/winter sports, etc. but there's also lots of room to grow as its still sort of on the fringes over there like what hockey was in Florida 30 years ago. It is also a fairly big, wealthy country that could contribute to the NHL's business in the not-too-distant future.
China on the other hand? There is basically zero hockey infrastructure, and will rely on dual Canadian/US residents to fill their roster. It will be a 2 week show of the best talent and then hockey will never be spoken of again. What will build interest in that country for the future will be a domestic league that is competitive and then have them start developing some players who can get drafted, compete in Canadian juniors/US college and finally make the jump to the NHL.