The polyphony is not really an issue, 32 notes is enough, you will never notice a drop out.
The piano tone, the action, and how they behave is most important.
The Yamaha is considered the best in its class for pianistic behavior, i.e. action, tone and dynamic response.
All use triple strike samples for their piano notes except the P60 which only uses a single strike, therefore it has less expression.
Gear owned: Yamaha P250, P120 and P90. Stand: Quik-Lok WS-550
EV SXa360 powered speakers