Oh, I agree that the Baby Bass swings like a rope. Those big strings, that hollow drum-like sound, it beats the pants off the electric bass. But frankly I don't know if it's worth spending $1500 - $3000 for extra resonance...not unless this particular gig starts paying more money and quick. But I suppose that is a personal decision.
What enrages me is the unenlightened traditionalist aspect--they want the Baby because it's "the tradition," which is usually a nonsensical argument. Also, as you point out, they want to SEE the upright...what the hell do the dancers care, as long as la clave tiene mucho swing, loco. Grumble, grumble...
It's reminds me of a story I read where Stu Hamm was called to audition for a gig in Hollywood (with Cher, was it?) and the first thing they asked him was, "So what do you look like?" I suppose anyone meaning to play seriously has to accept the shallow, pathetic nature of the entertainment industry.
Cheers!