The debate rages on. The two side will never come together. Budget matters, and what you start with in parts will matter. Headers will make more power. In the end build what you want.

If you want to build a 475 hp exhaust manifold std stroke 440 with iron heads and pump gas, no big deal. If you want 525 hp, you should probably use headers.

If you want to build a 550 hp exhaust manifold stroker with aluminum heads, no big deal. If you want 625 hp, you should probably use headers.