Tubular, square, etc... The thing about exhaust that builds power is the way the runners are tuned, the length of the runners & the way the collector is designed. It doesn't matter whether it is in a header or a manifold. The designe & flow is key..
We have used lighting, we are also a distributor for them. Not a bad product, but if corrosion is a concern then you must use the full stainless ones as the standard ones are ss inners & mild NON stainless steel outer pipes..
IMO.. If I was a consumer I would also ask myself what substantiates the best header, manifold etc.. Who & what substantiates the most power gains? A dyno or a simple it makes the power because the manufacturer says is does but doesnt back it with a dyno sheet?
Again Nothing against the other exhaust systems who's ever they may be. They all have their good points & bad. Headers do have their place as I said before, they can also rot, crack, etc.. Manifolds are not prone to cracking @ the flanges & they can hold up quite well to corrosion, or at least better than non stainless steel.. In the end one must go with the exhaust that will best suit thier needs overall..