I can't comment on the Andaz Gangnam breakfast but I stayed at the Grand Hyatt Seoul and Park Hyatt Busan (both on the Hyatt Privé rate).

The GH Seoul restaurant gets BUSY in the morning. There are a lot of breakfast stations with different types of cuisine but there are also a lot of people. PH Busan on the other hand felt more intimate. Breakfast is served across different floors and the tables are in different sections/rooms so it didn't feel as busy or loud as the GH. I think there were more food options at the GH Seoul, however I really liked that there was an a la carte menu at PH Busan. Having said that, the a la carte portions are small.

Some of my photos from the PH Busan. (Don't judge me for my food choices. I have to try a little bit of everything for my clients. That's my excuse and I'm sticking to it!)