Steinway Model M vs Model O
The Model M and the Model O are Steinway’s two most popular home grands, so most buyers choosing a smaller Steinway are deciding between them. They are close in size, which makes the choice easier than it looks.
The difference in a sentence
The O is about three inches longer than the M, 5 feet 10½ against 5 feet 7, with longer bass strings and a slightly fuller, rounder tone. The M is a touch more compact and usually a little cheaper used.
Tone
In a straight comparison the O tends to have the edge in the bass, because the longer strings give more depth. The difference is real but not enormous. In a small room you may barely notice it; in a larger one the O opens up more.
Size and price
Both fit a normal, generous room, and the M’s slightly smaller footprint can matter in a tight space. On the used market the M is a little more common and usually a little cheaper, though good Model O and Model L pianos are also plentiful.