so why use the sturmtiger when you can choose many other tanks that have more rounds and can go faster?
semp
The Tiger I is about 3 mph faster, so it is not a night and day speed difference.   The Sturmmörserwagen 606/4 mit 38 cm RW 61 is a seige gun and could 
possibly (I know some of you get hung up on words) level a town faster than a MBT.   So therefore, comparisons would pretty much be null and void.   The Brummbär would be neat, but maybe if the Stug III had a place in this game, it could be a 
fun weapon.  
I always thought the point of this game was to have fun?