I had the Fat Cat with ghost pipe on my '07 CVO Ultra with 110 motor early on mainly to help reduce heat. Early 110s were VERY hot - they have gotten better. This was before the cross under exhaust and the bike still had the older style crossover exhaust to the left side. So my co-rider couldn't get away from the heat. At least with the D&D it was all on the right side so she could shift over a bit and said it was better.
But they are LOUD and even though we wear ear plugs she hated the Fat Cats.
They did move the heat to one side the motor but the exhaust was still hot! I'm not real tall 5' 8" but I can flat foot my ultras with no problem at all but I had a tough time 'bow legging' enough at stops to keep my right leg off the pipe. Burned through several rain suit pants because of this and even burned my leg a couple times.
My Fat Cat header cracked at the weld after a few years. D&D was stand up about it and replaced it free of charge even though it was out of warranty. So I give them kudos for that.
One thing you might want to check on is the placement of the bungs for the O2 sensors. My '07 had the older 14mm sensors but from what I later determined I think the bungs were too tall and didn't allow the sensor probe to be deep enough into the pipe to properly sample the exhaust flow. This has been a complaint about several after market pipes from what I've read.
So performance, yes, noise, yes, and I found them difficult to keep my leg off when stopped. Personally I wouldn't want them. JMO 'cause you asked.