I used .3ds files because they did a great job with transformations and rotations, with .b3d, everything needs a bone.
I don't know whether Minib3d does too as I don't have BlitzMax yet. But with standard Blitz3d the .b3d format can be used for hierarchial mesh animation or rigid bodies as well.
E.g you can use the B3dpipeline tools to export an animated mesh without bones to a .b3d. This will animate perfectly in Blitz3d.