First, I wouldn't buy a bass for a one-off gig just because my band recommended it. Second, for any acoustic set, I'd just bring my fretless (my band actually suggested that, so they are cool with it), even though I have an acoustic/electric (see all the feedback and ergonomic differences pointed out in prior posts). Third, I really enjoy having an acoustic/electric around, it's fun to noodle on when you have a few minutes and don't want to mess with an amp. But the caveat is that I got mine super cheap from a buddy, so it was a bit of a no-brainer deal. I wouldn't go drop $1,600 or something on a new Martin just to have to noodle in my practice room, and probably wouldn't drop $500 on a new Fender/Ibanez/etc. either.