I play Selmer tenor myself. If you want a great, top of the line horn, the Series III is a great instrument. I haven't tried the new Supreme. I've been very disappointed in the Selmer student line lately.
For my school, I buy Yamaha horns. The EX horns are amazing, much less expensive than the Selmer, and sturdier. For bari, Yanigisawa is my preference, but the Yamaha 62 bari is an awesome workhorse for school use.
When I bought my tenor in the 90s the price was much more comparable, and that was before the Yamaha EX models came out. If I were buying today, I would almost certainly buy a Yamaha EX or a Z. If you have money to burn and want the name recognition, go Selmer.
For marching, we have a variety of older horns for kids. Mostly Yamaha 4xx or 6xx models. They've changed model numbers over the years, but anything starting with a 2 is a student line, 4 is intermediate, 6 is professional, 8 is "custom."