Certainly there's a 
personal aspect to piano sounds that will have 
very few of us agreeing on what works for us.
 I prefer Yamaha's nicely balanced and richly harmonic piano sounds to the wooliness of what's on other arrangers/digital pianos, and I'm very pleased with how they (Yamaha), not only stand on their own for solo work, but also sit
 perfectly in a mix for combo playing, or 
for use in an arranger.
  Not having played Korg's top and mid line PA-series, I can't compare their sound with what I love in the Yamaha instruments, but I have spent considerable time on the other 
major brands, and they just don't have 
anything to compare.
  As far as "favorite" pianos on the Yamaha Tyros-series, my "go-to" piano is still, and probably always will be, the 
Live!Grand Piano. Terrific punch, and a nice long decay, and yet lots of warmth for ballads or jazz...plus, a little tweak on the filter brightness knob (-12)and there's even more delicious warmth if you want it.
  The
 Live! Concert Grand Piano controversy wasn't surprising to me, as it is perhaps my
 least favorite piano sound on the Tyros3 and Tyros4...in fact, on the latter, it isn't even included in the "Main" panel pianos, having been bumped to the 
Legacy folder, and replaced by the new 
Super Articulation Concert Grand, a 
substantially better voice (in my opinion), but, still not as useful, or as "good" sounding as 
my favorite, 
Live! Grand Piano.
  I'm also very pleased with
 Super Articulation Pop Grand, 
SA Ambient Piano, 
SA Cocktail Piano, and 
SA Piano Orchestra. 
  "Piano sound" 
discussions are always a series of posts containing very
 personal ideas (and ideals) of what constitutes a "great" piano sound for each of us...what pleases my ear, may not work for someone else, and what sounds like steel wooliness to me, may be someone else's concept of a perfect tone.
  It's simple...choose what suits you...I know I did, and I'm totally content with my choice. I like the Tyros3/4's (and the CVP's) pianos 
even better than what's on the Motif line, and since they (the latter) seem to be working for many great players like Stevie Wonder, and Doobie Brother, Mike McDonald, I think I'm in fine company.

    Ian