I've owned a few sets of BFG MT's and driven them extensively in the wet, snow, ice and offroad in challenging mud, rock, abd sand conditions. I've also had the good fortune to do this back to back with BFG AT's and Good Year Duratracs. The MT's are just plain awesome in mud and loose dirt and provide extreme durability against sharp rock (running trails in Moab). On the other hand in the wet they are floaty and loose and generally lack bite without siping. The MT's are also a bit heavier and have notably more rolling resistance. With the torque of the Sprinter it's not going to be a huge deal but will cost a little fuel economy.
The BFG AT's improve markedly over the MT's in the wet, snow, and ice at the expense of mud performance. The achilies heal of the AT's is the rapidly deteriorating performance past 50% worn.
Finally, the Duratracs beat both the AT's and the MT's in wet, snow and ice and maintain exceptional traction well past 75% worn. In mud conditions they are a bit better than the AT's but not up to par with the MT's. The Duratracs do then to wear close to the pace of an MT lasting roughly 40-50k miles depending on how you drive. The AT's will commonly go 60-70k but the rubber is so hard past 50% worn that they don't perform near to the level that their tread depth would suggest.
Both the AT's and the Duratracs carry the snowflake extreme weather rating. The MT's do not.