TromboneChat

thatme, for me it works good to practice both instruments every day. (For me three or four instruments) Basstrombone and tuba work often on the same stuff, same music, scales, arpeggios and so on.
Actually its the same with same on small or large tenor, it is not enough to practice a lot on the bass, when it is time for the tenor you are no good if you have not been practice on the instrument you have to perform on.
If you don´t like the tuba, wait until you are shure, and the sell it.
I allways start on my basstrombone, high and low, tuba, high and low, tenor high and low. No tsure about what is best for you. The same rim is no option for me.

To follow up on both the current question and the OP's issue:

Find your home base, and work out from there.
I'm paraphrasing Sam Burtis (Sabutin - around the web).

There's a bunch of great advice earlier in the thread.

There's probably one horn that sounds right and feels right when you wake up.

It probably involves a particular bore, and a particular mouthpiece.
Figure it out.
Start on your home base, make the stuff work, then make the other stuff work.

If there's a particular gig coming up, by all means do whatever you can to make it happen.

Doubling is possible, but not easy, or necessarily fun.