The power difference between the X-pipe and V&H will be negligible. I would go with the ceramic coated X-pipe. Regarding power, the best power is froma a two into one like the D&D's. But bthey will be even loader than the true duals. The 2-1-2 will offer a little better power than the true duals but I doubt it would be noticeable.
It is a preference between looks power and cost. My buddy has the new D&D Fat Cat with the "quiet baffle" (which is still loud) but the performance is noticeable. I have the cat less 2-1-2 Rineharts with a lot of quiet baffle material (installed when the pipes were new) from Fuel Moto added for noise.
Need a Stage I AC and a fuel management system. With the X-pipe, I would go with Full Sac's TTS map. Fule Moto has a Carbon Fiber Dyno tuned muffler that looks great but I have never seen one since it was recently introduced.