Maybe I missed it in the posts, but are you comparing 2 pianos that are the same make and model and age except for size? If so, get the bigger piano unless there really is something wrong with it in your mind. Bigger is almost always better sound-wise and touch-wise in similar models. Now, if you are talking about the top-of-the-line model 5' and the promotional-grade 6', that is a different situation. Or if you are comparing 2 different companies, the smaller grand could be a premium model and the larger one a less-ideal model. Apples and oranges, right? It might help all of the posters if you were specific about maker, models, age, etc. You said you were looking at Korean pianos? I know some of Young Chang's pianos are built in Korea, but their lower models are built in China. Not sure about Samick. Probably similar situation. Wages in Korea have gone up a lot in recent years so the premium pianos are still built in Korea, but not the entry-levels.
2004 Mason-Hamlin polished ebony BB.
Working on jazz standards and Chopin nocturnes, preludes, and mazurkas (the easier ones.)