Square-bore vs. spread-bore?

Hey guys, what do you think works better: an Edelbrock Performer or Performer RPM spread-bore intake manifold with a spread-bore carb like a Thermoquad, or an Edelbrock Air Gap square-bore manifold with a Quadrajet or the equivalent carb?

Why do you think the Air Gap manifold is manufactured only in the square-bore configuration?

I've always wondered about this, so figured I'd ask. As always, thanks a lot.

(Corrected after RammerJammer75 pointed out my typo.)