I would suggest bypassing a Japanese import piano all together and getting a Steinway or a mason and hamlin (especially if you want to get a grand piano). Both of these piano brands are high quality and will provide you with years of enjoyment..... However if you insist on getting either a yamaha or a kawai I would recommend a yamaha. I own a yamaha upright and it sounds great and has had very few problems
Kawais have a soft, round, underwater-ish tone and sound almost like toys. Yamahas (especially the better uprights like the U1, which is great) have brilliant string resonance and great tones.
