It depends on the song. That's why they give us a switch. :mrgreen:
Seriously, if I were just a set-it-and-forget-it guy, I would have bought a Marshall. The reason we buy these switch-happy amps from Randall Smith is because they are so tweakable. If you're going to spend that kind of money, IMO it should be more than a one-trick pony. How I set that particular switch depends not only on the given song, but also on what other equipment I'm using.
If I'm running a fat but dark overdrive in front, I might be more likely to use Bold to give the bass some percussion and provide some headroom. If I'm running an OD with a tighter bass, I might use Spongy to give it some lushness and a fuller harmonic bloom.