Robbie Rhodes is right about concert performers playing a piano harder.
It would do no good to pound a baby grand like the concert grand is
played at times, because its power tops out and then playing it harder
would not increase the power.  The very reason the concert grand is
larger is so the artist might take advantage of both its increased
power and dynamic range.

I have placed a baby grand on a stage, and even though it was a
Steinway model A, it needed amplification to be heard throughout the
hall.  Whereas, the concert grand has carrying power.  It's not a
"loudness," as much as a volume, because even at low intensities, its
sound carries better.

When I was retrofitting a 9'6" Knabe with an Ampico system a few years
back, I wondered how it was going to sound in the relatively small room
that I had to regulate it in, but it was just normal.  It didn't "blow
you out of the room or anything."  But after this piano was shipped,
I was called to regulate it in the hall it resided in, which was huge,
and that piano made the rafters ring!

A baby grand, even at double the pump speed and settings maintained
by the large grand, would have been lost, but this instrument was a
powerhouse, partly due to the fact that it had been specially chosen
years ago by artists commissioned by Ampico to visit the Knabe Wareroom
and chose several concert stage grands especially (there are 3-4 grades
of pianos in the concert class.  The best ones would be chosen at the
factory).

Because the concert grand has much greater dynamic range than a baby
grand, it likewise has to have much greater vacuum pressure to provide
a realistic performance.  This is why the load on the components will
wear one out much sooner, because while the mechanism is the same, the
pressures generated are over twice that found in a baby grand.  It is
wise to change the amplifier ratios for the concert grand to take the
load off the mechanism when such ripping power is not needed.  Musically,
it will not make any difference, but mechanically, it will extend the
life of the instrument.

The stack of an average concert grand may need to be up to four inches
longer than that of the average baby grand, so the hardware is scavenged
and a new stack is built.

Craig Brougher