I'm arranging a lot of music at the moment, and I find it difficult to combine tuba and electric bass. For most parts, I just make them equal with very few exceptions. For example, I do make them different when I want to reach a very low note that are impossible on the electric bass, or if a part simply becomes to difficult on one of the instruments.
Keeping them exactly equal has some pros and cons. For instance, if one of them cannot show up to a gig, it's very good to have redundancy. But if they are not perfectly in tune and tight in rhythm, it sounds a bit muddy.
So if we consider the case where we have both of them. Can you give any general guidelines for how to combine these two? I don't really know how to think here, because one of them will be forced to play in a way that is not really typical.
I might add that the full setting includes trombones, trumpets, saxes, clarinets, flutes, banjo and drums.
We do not have a bass trombone. Just regular ones.
Tuba and electric bass are the only bass instruments, and we only have one of each. The music is primarily jazz.