Remember back when you were a kid you would go to Grandma's house and she had that little upright piano sitting against the wall? Most likely it was a spinet, and we got to bang on the keys and it was probably pretty out of tune.
Well today the selections are a lot better starting with vertical pianos of different sizes going up to the horizontal grand piano. Starting with the vertical types there is the tallest, fifty two inches tall, called a professional upright. Fortunately all vertical pianos measure in width approximately the same within about three inches. So if you have five feet of wall space, you have plenty of room for a vertical piano. The taller pianos are referred to as "professional uprights" because professional piano players demand better sounding instruments. Most piano buyers in the world buy vertical pianos becase of space limitations. Here in the United States we enjoy larger homes, so we can have the larger "grand piano" sizes. The professional uprights also have the same pedal functions you have on a grand piano, where the smaller uprights have limited usage.
If your question is why people prefer the taller pianos, the answer is quite simple. Every piano is equipped with a sounding board, usually made from spruce, and that is what is referred to as the speaker in the piano. So you realize that the more square inches of sound board we have, the bigger the sound will be. The other factor is the string length. Obviously, the taller the piano, the longer the strings. This means that the bass section of the piano gets fatter, and therefore produces a bassier sound. This provides more depth and warmth to the music.
The shorter the piano, the brighter and more tinkely the sound. Some people refer to it as tinny. So if you can afford the taller types of pianos, you'll enjoy the sound much better. The taller the piano, the more raw materials are in it, and the more expensive it becomes.
Now let's move on the other professional uprights. The forty eight inch upright is generally the preferred size used by most piano teachers and their students. When we were in school, most were equipped with what is called a studio piano which stands forty five inches high.
Lastly we have what is called a console piano. These pianos range from forty to forty four inches in height, and are available in a huge variety of furniture styles. These pianos are generally used for entry level students and are most affordable.