MHR BigBore exhaust for Bigbore 77 and 97cc. No good?

I see alot of people ask what exhaust to buy to match the 2 bigbores 77 and 87 from Malossi. None of them seems to reccomend the MHR BB exhaust. Why is this? Is that exhaust no good? They rather reccomends the Roost 77 or 87 exhaust,C30 form Yasuni or some other brands..

You should think that Malossi would make one of the best exhaust for those cylinders. At least i would think so.