I picked up a 99db DASA for my YFZ. The header is a bit bigger than the HMF, and is 3 stepped instead of 2 stepped like the HMF. top end power was about the same, however, I felt like the DASA would leave harder than the HMF and was 1-2 lengths quicker by the end of the ~500-600 foot drag area at SL due to that. I would say the sound output was about the same, although I didn't have the sparky in for the DASA.
Some of the tubing welds on the DASA were pretty iffy. When you looked on the inside, it looked like bird shit lining the welds, which definitely hurts flow. The system looks really nice, and the header fit much better than the HMF

yea yea I know that was a mistake on 10 headers. All in all, they are pretty close, and I think the HMF system would be the clear winner if they'd get me one of their Prowler head pipes for the comp can which would let my built motor breathe a bit more.