I also have the Akrapovic 4-2-1 Titanium Carbon full system and luv it!! Feels like a whole new bike.
If your looking for weight saving go with 4-2-1
If your looking for the dual look go with a 4-2-2
I think both have the same performance with a slight advantage to the 4-2-1
You cant go wrong with an Akrapovic the quality and workmanship are world class and the welds are perfection!!