I would certainly choose to pay in fiat if the resultant price is lower and the service the same as in your example with airlines and online booking but in my experience when it comes to food Bitcoin accepting outlets are well above average in value and quality.

Online air travel sales are ultimately big business and any middleman must pay the airline in fiat so that is not the type of business i would expect Bitcoin to have any significant advantage- in fact airlines are almost always themselves highly debt leveraged and effectively owned by either the banks or governments if not both.

Smaller local grassroots businesses who are accepting Bitcoin are my preference to support and my experience with them has almost always been very good. When traveling to a new destination it helps to narrow down the often overwhelming number of food outlet options significantly down to a manageable few.

How many restaurants in Hong Kong accept Bitcoin? My guess is it would be in the single figures- so go out and try them!