The Jet Pro is made in the US and the DDM is made in China, I don't know if that makes a difference to you or not, but to some people that's a big deal.
I have JP rear outlets on my FG's and a side bleed on my XB. My FG's sound like 125cc dirt bikes, but the Jp on my XB sounds like a snowmobile. It actually rumbles the ground the same way a sled does.
I had a DDM years ago, but I sold it after I bought my JP. I just didn't care for the sound of the ddm, plus I like the look of the welds on the JP. The welds help to hide scratches and dents. Something of which sticks out like a sore thumb on the ddm.
If you manage to bend, twist, kink or otherwise deform the Jet Pro, Dino will fix it for the cost of shipping, you can't beat that!