I can't think of anything that can compare to the Roland RD-800 and now the new RD 2000 in sound and real piano feel. I have played them all and to me Roland is the best stage piano.
Also : Roland FP 90, Kawai ES8, Kawai MP11...
It highly depends on where he needs the digital piano for?
Does it need to be just a piano with great piano sounds on board?
Does it need to have build in speakers?
Or will it also be used as a Masterkeyboard in a rig setup?
Is weight a factor into the decision?
Would you like to be able to edit and fine tune your sounds?