I'm try to decide between Fullsac or D & D. 2013 CVO RG. I ride 50/50 around town, trips 2 up.
D&D 2 into 1 will produce more HP when properly tuned.
Fullsac will also produce more power but if you use the power cores in a 2 into 2 configuration, probably not as much as the D&D.
The Fullsac won't be quite as loud as the D&D but you have a choice of 3 different size powercores.
Best of luck.. these decisions are always sort of a preference issues.
I run the Fullsac with the 2" powercores. I really enjoyed them at first. Now they are sounding a bit loud for me.
I would never have gone with the 2-1 from D&D just cause of the looks, regardless of how much extra HP they'd give me.
And my buddy's D&Ds are damn loud, almost as loud as Rhineharts but not as pitchy.
DH