One reason I got into them is that I can try out different aspects. I'm a comeback player was just really curious how different instruments perform. The Mauriat 600 is heavier, the 655 is a large bore, one of the Carols has a lot of nickel and plays bright, etc.
I also found as a doubler I just really enjoy the flugelhorn and the piccolo. Honestly a lot of us who play are doing this just for fun, so we have a different relationship to gear than professionals, who need something standard that can be tweaked.
I haven't compared the Jupiter professional vs intermediate line, but am curious. I really like the 1100 flugelhorn and found it easy to adjust to. I'm curious how their 1600 line plays.
Harmonie does make their own valves, I believe. On the local facebook market there are two for sale and I've met Canadian players in Taiwan who really like them. Mine I bought 2nd hand and I like it. I'm curious what their market/model is; I think they make for the domestic market under their own name and also design horns for international makers.