A friend of mine does this all over Europe.
He has used B3, MD500D/, 407, and currently with a Llama which is still the best machine.
B3 you cant see out of it.
MD500 no hot and high capacity and annoying in the wind as the saw is directional you don't have a choice.
407 was not so bad - maybe needs more engine power.
315B is the king but how much longer will it viable with support? Not much longer by the looks.