This doesn't directly answer your question, but it'll give you something else to think about. IMO, the value of a six pak is the wow factor at a show when you open up your hood. Aside from that, I doubt you'd be able to gauge the difference on a "butt dyno." If I recall correctly, in the quarter a 440-4 is .2 seconds slower than a 440-6, if both are in stock form. In other words, if money is an issue, consider rethinking the six pak option.
Also, it's clear on your other posts that you're also somewhat interested in handling. A big block adds a couple hundred pounds, which sits up relatively high. Personally, I'm a big handling person, and having driven both I can feel the handling difference between a big block and a small block. You can stroke a small block to produce some serious power without the weight gain that comes with a big block.