Ive swapped from a Schroeder 1212L to a BB2 and there seems to be a world of difference. The BB2 seems to be less coloured, certainly compared to the 1212L Some might like that, i must admit ive had a love/hate relationship with the 1212L for a few years. No question it did the job but one thing ive noticed now is that i can hear more of a difference between my basses. Before i felt the cab made them all sound pretty similar. There is more clarity and definition in the low end with the BB2 and even the very lowest notes have some growl, something i really struggled to get with the 1212L.
Going from the lowest notes to the higher ones there seems to be a lack of mud and more clarity on each note. Before i fond notes were blending together more, depending on the room/stage.
I had a Streamliner for a few months and really struggled to get on with it. It just seemed to be a bit too "big" for the 1212L, especially on hollow stages. I just couldn't tame it. This was coming from a MB SA450. I ended up getting a MB F1 head and ive had it for a good few years now. I think the MB tone is quite bland and lifeless compared to some heads, but they give a good starting point without too much of their own personality being overlaid.
Thats my thoughts anyway.