Had a friend of mine who had both and he could not get the d&d to work at all. When he purchased a SLP kit that machine seemed to take off and perform like it should. Not a speedwerx kit but close i have rode a m1000 with a speedwerx kit and very similar to the SLP . speedwerx all the way! my 2 cents.
Does arctic cat not own part of speedwerx....I heard this, dont know if its true but i know speedwerx has AWESOME customer service and they do work very closley with cat to devolop there cat parts. If i were to buy a pipe it would be speedwerx .
For trail, drag, snocross, and CC I would say either Speedwerx or D&D. For mountian sleds it seems SLP is building quite a reputation for good performing, reliable stuff.
i would not buy another d&d product again i have had few of there pipes and cans every one of them cracked and leak exhaust , in my opinion they are junk , but they did warranty 1 of the cans because it cracked @300miles on an 09 m8
I have a speedwerx y-pipe and main pipe with an mbrp can real good top end power in my opinion the slp pipe is the better mountain pipe my buddies are all runnin it on there m8's and love the setup! Speedwerx would be my second choice for real good pipes so ya slp then speddwerx