This is more of a question than an answer, here goes. Wouldn't the real deciding factor be the cruise load, rear gear, and rpm, along with engine size? I doubt one size fits all, so a torque monster like a 572 or bigger might be happier with a 9.5, and a 318 in a light car like an early Dodge colt might like a tight 7 inch. By your screen name it looks like you are in the middle, like most. If I were to put my 528 into the street car, I would bet on a tight 9.5.
There must be a general rule of thumb like the K factor that would decide which way to go. Each size core must have a minimum (tight) K factor it can be built to.