Often times, the answer boils down to how well a given piano's action is regulated to be even-sounding across the keyboard:  (Assuming all are in concert-ready tune; if not, can it be tuned in time for the performance?) Are there any notes which seem to stick out? or are some notes dead sounding?  Is the action too heavy?  Is the escapement regulated such that the piano is capable of producing fast repetitions of a single note, if required in the repertoire to be performed?  Do the pedals work smoothly without any mechanical squeaks? How well does the piano "project" the sound into the auditorium?
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Cheers,
Joe

I agree completely and that's why I prefer my Casio PX-150 driving my now modified Pianoteq 6 Model B to my friend's acoustic Baldwin parlor grand.  Her instrument is a beast to play.  The action is quite heavy, and the hammers are hard.  She so tight, she refuses to spend money on tunings, regulation or voicings.  She thinks the world of the thing, but I'll take my Casio / Pianoteq any day over it.  The Casio action is fairly light, and of course a well tuned and hammer voiced Pianoteq Model B is absolutely lovely and easy to play with expressive nuance, even at low volume levels.

It's also possible the piano was dropped or otherwise mishandled in transit, and the carrier simply said nothing of the incident, and hoped nothing would come from the incident.

Given a choice of instruments from which to choose, something that comes down to the pianist's choice in selecting a piano for a concert is this question: 
"Relatively speaking, how hard do I have to work to make the sound I wish to create?" 
(Remember, sometimes the visiting pianist is provided only one choice of a piano in a concert hall, and (s)he must make do with whatever instrument is available.  Glenn Gould used to complain about the deplorable pianos he was called upon to perform. But then, that was GG, and the pianos were probably much better then the performer had described them as being.)

Often times, the answer boils down to how well a given piano's action is regulated to be even-sounding across the keyboard:  (Assuming all are in concert-ready tune; if not, can it be tuned in time for the performance?) Are there any notes which seem to stick out? or are some notes dead sounding?  Is the action too heavy?  Is the escapement regulated such that the piano is capable of producing fast repetitions of a single note, if required in the repertoire to be performed?  Do the pedals work smoothly without any mechanical squeaks? How well does the piano "project" the sound into the auditorium?

Concert grand pianos are designed to project the sound to the listening venue, eventually to the audience.  Pianists must make sometimes subjective decisions based on where they are seated, namely, at the keyboard.

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An anecdote:
In the spring of 1970, I had a rare opportunity to attend a concert by Arturo Benedetto Michelangeli in Chicago's Auditorium Theatre.  He used to tour with his own Hamburg Steinway whenever possible.  As it was a long time ago, and I don't know the details, but in the first half of his concert, there were a few notes that didn't sound quite right -- they were in tune, but something wasn't quite right.

During the intermission, the piano technician worked on the instrument, and the artist tried to live with the adjustments.  In the end, they pushed the piano off to the side of the stage and brought out a different piano (assuming it was another Steinway D, but I was too young to identify the instrument -- advertising was not pasted all over the sides of the cases in those days), and ABM finished the concert.  The next day, the Chicago Tribune newspaper review mentioned how pianos were swapped during the concert.

Cheers,

Joe

For a blind test of these 3 pianos (real) high level recorded under the same conditions.
(In a different order from the original Youtube video - unfortunately in a destructive file format, but not that much) 3 pianos: Bösendorfer 290, Stenway 274 and Yamaha CFX, with the same pianist.
There are actually 6 excerpts, (for these 3 pianos), including 3 with a voluntary cut in the treble, with a fall of 80 db at 14Khz (to test the ability to take or not account for higher frequencies) . The high mp3 translation of the original recording usually causes a significant weakening of the level of frequencies above 16Khz (see spectrum - after translation in mp3 - on the photo)
To try to imitate them with software, today I will give my trust to Pianoteq in its ability to allow all (soon?) To reproduce them in a very convincing way. Personally I can judge this live (and with many limitations) only in the case of Bösendorfer, using a model 200 daily, not having the opportunity to play (or hear live play) on Yamaha CFX or Stenway D 274.

A good reason for the creation of new .fxp Pianoteq 6, especially for Bösendorfer and Yahama CFX?

https://www.youtube.com/watch?v=T2GYYV8JSqM

Even better to watch if you have very good sound system and no one around to complain about.