Ok, I suppose this has to be more exact, obviously everyone wants both, but doesn't every choice show a priority?
When do you know a piece is 'perfected' and doesn't need further work? How much should it continue to be maintained, if at all?
In some pro pianists, great ones, I hear some stunningly average performances from a technical standpoint, and in the pieces they program often, I uniformly hear stunning performances.
This leads me to the conclusion that every piece they work on isn't prioritised the same.
Actually, I think most of it has to do with motor-memorisation.
Most pieces in an advanced concert pianists repertoire are generally memorised in a different way. To give the best performance, it has to be memorised as a set of motions, as opposed to a series of notes, if this makes sense.