I'm not saying quality on one is better than the other, but I would argue if anyone said their DPs were higher quality than Fenfab. Brett doesn't cut corners. Materials of construction are top notch, welds are done right (purged), and his craftsmanship is top-tier. You won't go wrong with Fenfab DPs.
After a few weeks of driving with the Thermal installed I noticed the tone did mellow down very slightly. I went back through and retightened all of the bolts and put some blue Loctite on them. A bolt on one of the tip clamp was coming loose pretty bad.