There are several inherit design advantages of any grand piano as compared to upright pianos.
The grand piano action utilizes gravitational pull to return action components to their original position quicker making the grand piano more controllable to bring out soft and loud passages.
Longer length keys provide better and more precise leverage for greater control in experiencing music.
The action assembly inside grand pianos have an additional lever component allowing each note to be replayed when the key has returned to about 50% of its original position.
Many grand pianos also feature a sostenuto pedal. By using this pedal, a pianist can sustain selected notes while other notes remain unaffected.
The soundboard design is optimum to allow each note of frequency to have its own properly sized soundboard. In a sound system, this would be the equivalent of having 88 different sizes of speakers.
Grand pianos are designed in different sizes for different uses. All grand pianos are very close to the same width (56″ to 58″) and height, but they vary in length from as small as 4’5″ to as large as 9″6″. This is the measurement from the very front of the grand (at the very front edge) to the very back end of the curved rim.