I have been giving this alot of thought lately. Yes, I have taken for granted the benefits of the breath builder and the breathing bag for many years because it has benefited me and my students so much. This is a good oppotunity to articulate some of those benefits to others who don't know the devices.
One of the debilitating things that happens to players in regards to breathing is tension. Even if you can get a student to take in a huge amount of air it often comes with a price - great tension in the entire upper body and throat. Its obvious how detrimental this is to sound and many other things.
The breath builder helps train you to move wind in and out in large capacities without this tension. It trains the body to accept lots of air and let it out freely without strenuous effort. Now, this isn't necessarily the way a lead player or high note guy would produce sound... its sort of the opposite of the "wedge system", but it is a great way to make a good, solid sound in any genre.
If you or your students play with alot of throat and body tension, I recommend the breath builder to learn to move wind with "minimal motors"... or the least amount of energy.
I also recommend that you use exercises to learn how to hold your breath with the throat and nasal passages wide open. This helps you learn to deal with lots of air in your lungs without closing the glottis while you play... again, helping with a closed and tenses throat. Most people when they hold their breath, keep the air in by closing the throat.. try to do it with the throat open.. it ain't easy and it can creat tension if not panic. The best way to do this is to develop the feeling of continuing to breath in as you hold your breath. This is a great exercise for developing a relaxed body during respiration of large quantities of air.
Michael - studied with a 53 Studebaker