Before I switched to Adams euphoniums I played a Sterling Virtuoso. The Sterling had a floating leadpipe. The Adams has a soldered leadpipe. Conventional wisdom says that a floating pipe frees the response but takes away a bit of the tone's solidity. That doesn't match my experience with these 2 horns. When I first considered switching to Adams I made an extensive A/B recording and had several trusted colleagues listen to the unidentified comparison. Most liked the Adams, but they all said the two were very close in sound. In playing, I found the Adams had a freer response and one of my colleagues noted that the Adams horn gave me more freedom of expression in one place (not know which horn it was).
So that little test would knock holes in the conventional wisdom I mentioned. However, I was comparing two different brands, which introduces all kinds of other variables. (The one consistency is that my Sterling and the Adams used the same valve set, which has an effect on how a horn plays). My conclusions are:
1. My tests don't totally disprove the conventional wisdom because of the other variables. I believe a floating leadpipe would respond more freely, based only on logic. Whether that would have a good or bad effect on tone...I can't rely on logic to say one way or the other.
2. Because of other variables between brands, or even models within the same brand, I would not "go shopping" for a horn with a floating leadpipe.
In other areas where I had some experience/expertise, like shoes, cars, and stereo gear, for the most part you needed to go by the total result, not by the presence of a feature that "should" improve things. It's the same for horns. I don't personally care how my leadpipe is affixed to the bell - I just want the horn to make it easier for me to get the result I want out into the room.