As far as Conn goes the earliest horns I have are top sprung from my 1906 Conn-querer up through my 1928 2B. Then at some point they started producing many models with the bottom sprung style with a top guide plate and pin using a very short broached slot no longer than the top sprung broaching.This was used in Victor model trumpets and cornets for many years. This was used in my 80A Victors 1946-47-52 and my 1956 Victor 6A and B models. But the long broach I have only found in the student models like my 1957 Director trumpet and my 1958 Director 18A Coprion cornet. So it doesn't make much sense to say the top sprung models blew the bottom sprungs away or that the bottom sprung style is old school(top sprung is older) or that the long broach was too hard or expensive to make (since it was used in the cheaper student models) or that the bottom sprung is noisier than top sprung. The Victor style bottom sprung are some of the smoothest,quietest valves I have felt/heard. I see no advantage or disadvantage to either style. As has been said before the advantage is to be found in the quality of the workmanship for either style. I have played many top sprung horns that the valve action was no better and in some cases much worse than the long broached bottom sprung Director models. But Conn did continue to make some models with the top sprung design, in several different configurations, all through the years that they produced bottom sprung models,They must have seen something positive in both designs. If you are getting a lot of noise make sure everything is tight and that everything is seating properly,top and bottom caps,finger buttons,stems if top sprung also check your top cage caps and on all models lube your guides whatever style they are for smoother, quieter valve action.