To fffreddy and azureblue....did you see this post?
http://www.talkbass.com/forum/showpost.php?p=9026692&postcount=36
Quick summary....MB210+115 was quite a bit louder and had more thundering lows than the MB212. As the MB212 breaks in, it is doing quite well in the lows department...actually I liked it more when the lows were a little more 'tucked' personally. I'm running the MB212 straight-up 'flat', whereas the MB210 demands to have the lows rolled off and the highs boosted for 'my' sound. The MB210 by itself strains a bit to deliver the volume level that an MB212 can handle with ease.
So for volume it's
MB210+115
MB212
MB210
in pretty much equal stairsteps.
Let me know what else you'd like to know.