The stock pianos in the Fantom and the Motif ES if played very carefully might be of some limited use but they are hardly for professional work. The Fantom suffers from incorrect EQing, dull bass section, hodge podge layers and poor programming that makes smooth velocity shifts impossible. Besides it's a small grand (less than 7'my guess). The Motif ES is too hyped in the bass section but if played only on the soft layers, doesn't sound too bad. It suffers from very unsmooth velocity shifts to the hard layer as well. The Triton piano doesn't count unless you're playing Cuban music (Pakito) where the sound of way too much laquer on the hammers is the effect you like. Lot's of traditional Korg aliasing included.

Third party pianos offer the only hope but all of the above units are pitifully slow in loading data. For example, the Motif ES takes 13 minutes to load a 250 meg piano. Slightly shorter for the Fantom.