I use a BBC stand for many of the reasons that have been enumerated in this thread. I still own a K&M stand (any offers?), but I abandoned it because it doesn't allow the tuba to be placed at a sufficiently low height for a short player. The BBC stand does, and I find the manner in which it folds up very practical for sticking in a gig bag without adding significant weight while carting my gear.
One of the advantages of using a stand was reinforced this week for me: playing different horns and adjusting the height of the stand's cradle for comfort rather than making any adjustments to the position of the horn, body, etc. I keep the BBC stand in its lowest position for my 4/4 Nirschl and for a Neptune that I recently borrowed, while, as one might expect, I raise the cradle for my 983. I was initially surprised that I actually have to raise the cradle to accommodate a 2165. For all its huge girth, the receiver on the 2165, with presumably its original leadpipe at its factory-set height, is closer to the bottom bow than the other horns that I've mentioned. Raising the cradle of the stand eliminates any need to make other significant adjustments in playing position.