Your post makes no sense to me.
You ask which of two brands is the better manifold to use as a tunnel ram and you say you already have one, but don't feel like buying two carbs?
Huh! Which ever brand it will need two carbs on it to work right. Don't even think of using one carb on a factory cast tunnel ram.
For most purposes you will be better off with a single 4 barrel single plane intake. Even the ebay Team G or Victor Jr, would be better in most cases than a tunnel ram with one carb on it.
Tell us what you have and what the principle and secondary use of the engine is?
In certain applications tunnel rams with big dominators is better at hbigh rpm and with high hp.
There is no such thing for sure as which is best. Maybe the one you have is best becuase you already have it.
If this is a street or bracket engine, (Low compression I see you are asking about) maybe a single 750 could be enough carb for you. WE have no idea what you have or are using it for.
Ed