As far as I know.... X marks the spot
For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine.
The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote the cylinders to vent exhaust gases more efficiently because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system.
In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved exhaust venting by smoothing out uneven exhaust pulses from the engine’s firing order. It also helps quiet down the exhaust, resulting in a mellower, less raspy tone.