I haven't been to Korea but have been to Japan many times. I don't stay at Marriotts there because I use the room to sleep and I rent a car so I can drive to different hotels and quite often the difference between a Fairfield Inn in Japan and a local chain is like 3x. It makes sense if you need a Western size room and bed. The biggest bed in Japanese chain is a 160cm bed in Dormy Inn. In general the Japanese hotel rooms are pretty small and some "double" beds can be only 110cm wide. I'm not tall at all so the local chains suit my needs.

Eating out in Japan is a joy, you can find great Michelin level western food down to 110 yen sushi/bread.