I have or have had most of the GT's still have the GT-3, GT-5, GT-100,
and have sold on the GT-8, GT-10, GT-6B, and GT-10B.
Yes the GT-10B is specific for bass with bass preamps (nowhere near as many as the GT-10) and some bass specific effects (multi band comp and wah).
I find the GT-100 beats the GT-10B (IMO) in the quality of the amps by a mile, the GT-100 has guitar type amps, but many clean ones are great on bass, and also has custom amp settings.
They are very dynamic and tube like, that has the let down for the GT-10B (and more so for the GT-6B).
If you are not using the GT preamps and effects only, then it is a fairly even race between the 10B and 100, the 100 has more effects and they are more refined, the GT-10B has the multiband comp (which never really did it for me) and the Wah is tuned for bass, the GT-100 wah is OK but doesn't quite hit the spot.
The Tuner issue is just on a low B of a five string bass, the GT-100 USB features are kind of gimmicky (the GT-10B still does USB re-amping).
The GT-100 has all those Accel effects too, but the are just a one trick pony thing too.
What wins in the GT-100 for me is the superb preamps, distortions (non fizzy), and the effects have a certain 'richness and quality' over the previous generation GT,
plus the dual displays which are easy to read, the GT-10B blue screen and lazer bright leds are hard on your eyes on a dark stage.
And I prefer the black paint job of the GT-100.