2x4 Question

I'm doing a little investigative work of which I cannot disclose
at this time.
What I would like to know is:
1: Of the offerings that are now available by other manufacturers
what are best and why?
2: What would you change to make a better manifold.
3: Any special features that would benefit or make such a manifold
interesting or valuable to a racer or street car driver.
Things like holley vs. eddy, distributor clearance, hood clearance, choke, water passages, port sizes, things of importance to a potential owner.
The smallest detail or need should be addressed.

The tunnel rams and STR series manifolds won't be in the mix at this time,
only single or dual planes designs.

Thanks Guys