I haven't tried all leadpipe and horn combinations, but to be honest have had no success with true "improvements". Different, yes, better, no. The hard part is a fair test. A leadpipe with braces soldered responds far differently than one without.
I have 4 after market leadpipes for my Bach 229HCL - and keep coming back to the original. I am currently trying a shortened Bb leadpipe on the C because with the tuning bell modification, I needed to move the sweet spot and that required a LONGER pipe. I still am using a standard Bach pipe. All of the aftermarket pipes destroyed the Bach core - which is what I bought the horn for.