As Scooby Tuba noted, if you WANT something different, then that's reason enough to BUY something different. I agree with this, as I've bought "something different" more times than I can count (ok, about a dozen over the years) -- rotary and piston, in every key (and in both silver and lacquer
Having said that ...
If you search the archives (use the "search" link at the top/center of the page) you'll find that the 186CC is universally accepted as a great, do-it-all horn. I've heard a number of college tubists soloing on different horns, and the 186CC ended up with the nicest sound of the group. It's a great, all-purpose tuba. And it's yours ... now!
Years ago, the big-name pro players (some of the more notable ones) played rotary valved tubas, and they were all the rage. Now it's piston valves. Go figure. The horns are all good quality, but there are subtle differences, granted.
If your horn is in decent shape, you have an excellent choice right now. But, for something different in piston and in CC, I would recommend the Miraphone 1292 over the 1291 for improved response (slightly different leadpipe and added bell garland). But these horns have a bigger sound than the 186, imo., if that has caused you difficulties in some settings (be aware).
Another reasonable, "do-it-all" tuba is the Conn 52J CC. It has 4 pistons and a rotary 5th valve. Many tubists I've chatted with think the Conn 52J / 54J / 56J tubas are rather "plain" sounding, however. I like my 56J, but your ears should be the judge.
Check intonation carefully with a tuner for ALL tubas you try out.
If you plan to be a music performance or education major, you should look for a good 4/4 - 5/4 size contrabass, most likely in the key of C. A bass tuba, while typically not having as full of a sound, allowing a less "overpowering" result, may not be what you want as your primary college tuba. (Eb or F tuba)
Look for a used tuba in good condition, as you can likely sell it later (if you wish) and not lose much money.
(BTW, you said the rotors didn't feel as smooth. Rotor valves in good condition should be smooth and easy to play. Could it be that one solution is to keep the horn and ask a competent repair person to check out the valves? Are they "healthy"?)
Random thoughts for your consideration,
(I vote to keep the 186!)




