Stuffy is a symptom. The trumpet needs a certain amount of inefficiency so that our air passes through the horn in intervals that keep us from suffocating, or running out of air too early. The other part of stuffy has to do with hearing ourselves. Everyone take their own favorite instrument and play in a nice sounding room. We get the warm fuzzies. Now take the same horn and go to some lake where there is a great distance between you and anything. Play the same horn and it is stuffy. Stuffiness is a combination of hearing and breathing. For environments without good acoustics, lightweight and lightly braced horns give the player more information back - at the cost of what the audience gets............ They are perceived as less stuffy.