The best header for any application is an "equal length" tube header. The exhaust pulses should not fight one another to escape. The design of equal length headers allows exhaust pulses to "line up" for exit out of the exhaust system as a cylinder fires. For example, when cylinder 1 fires the exhuast pulse goes into an exhaust tube, when cylinder 2 fires the exhuast pulse goes into an exhaust tube- and so on. If the tubes are of equal length, the timing of the exhaust pulses will have the pulses sequentially lined up and ready for a proper exit -- where they do not fight and bump into one another. If they fight and bump into one another - you get unwatned back pressure.
Long tube headers are typically not equal length headers - although with enough searching you can find equal length long tube headers.