When the listening environments are acoustically okay, in a home or in a demo room, it’s really not hard to hear and remember the main characteristics of that loudspeaker. I have actually never been surprised by the sound of a speaker I’ve heard before, they always sound close to how I remembered them to sound on previous occasions.
This can be a good way to compare, but don't forget that the audio chain involved in the recording process can color the sound as well, so how do you make sure the actual recording is a good representation of how the piano sounds, IF the only loudspeaker in the room is the one you are evaluating?
Another problem, unless the recording is very dry, is that you will get a “double effect” of the room acoustics when playing back the recording in the same room where the actual recording took place.