Hi Chony
Good to see an honest personal review. (Others will probably disagree as their personal preferences are different, but those with similar preferences will have similar feelings)
I must admit though I am surprised you place the build of the Yamaha above the Korg, as I myself have always found the Korgs to be a much more robust feeling keyboard. (I suspect however it may be ergonomics that you are talking about rather then build)
Hope you continue to enjoy your Korg, and can get round any of the idiosyncrasies you find. (Don’t forget that if you get the chance, also try Roland, Ketron, Wersi, Lionstracs, Bohm etc, as you may find one of these gives you the best of both Yamaha and Korg)
Isn’t it great to have so much choice?
Regards

Bill