I own short, medium, and long scale Alembics. To me the difference in tone is more determined by wood selection than scale length. For example, I have a short scale bass that I use as my main bass. Zebra wood top and back, mahogany core, maple and walnut neck. That bass sounds completely different from my other short scale with the walnut top! To me it is a night and day difference. I also have a maple topped short scale Alembic with a graphite neck. That one sounds like a whole different instrument altogether. Same scale length and electronics, but made out of different woods and a graphite neck.
My medium scale Alembics are the same way. My maple and mahogany bass sounds completely different from my Alembic with the walnut top and mostly walnut neck.
Of course strings have a large effect on the type of tone you get too. For example the difference between DR High Beams and DR Fat Beams on the same bass is very obvious. Then of course if you go to a flat wound it is a completely different vibe and playability.
I am not a very tall person. So I mostly use the short scale and medium scale basses. The long scale is just too much of a reach. I say to go with the one that fits you the best and experiment with different strings for tone variations.
As far as balance and neck dive, you really have to approach it from playing that particular bass. Not compare it to the way another bass hangs on you. It is a different instrument. I use the small body basses, but I position the bass so that my right forearm holds the bass perfectly. Neck dive is not an issue at all to me. I guess you could not do that if you are used to playing your bass in a lower position on the strap. To me the weight of the bass is more of a consideration than neck dive.
Michael