A balance or X pipe will help reduce the drone at 2500 to 3000 rpm and also reduce noise output at higher rpm and Ive always thought ute and van twin systems sounded a bit off because they are usually diferent lengths because of the fuel tank. The X pipe seems to sort that out somewhat.
As for power and noise reduction a single 2.5 with a couple of offset glass packs will feel snappier keep the neighbor's happy and still have a note.
Its only my opinion but I prefer a single system.