Excellent post. I've long thought the same thing, though you articulated it better and put the whole theory into the larger context of the two bands' respective musical universes.

It's occurred to me that this distinction (order vs. chaos) might be the thing that makes me prefer Phish slightly over the Dead. In many ways, I respect the Dead more than Phish. I think it's almost undeniable that the Dead were better songwriters, at least as far as traditional songs go (rather than instrumental prog-opuses). Say what you want about Tom Marshall, for example, but he's no Robert Hunter.

Still, when it comes to being really grabbed by a good jam, I've always been able to connect more with Phish, and I think the underlying sense of structure, of (usually) having a destination, probably has a lot to do with that. As you say though, Phish did at times struggle with an emotional barrenness and an overly geeky sensibility in their early improv, and the Dead never really had to overcome that. Perhaps that's why it took Phish so much longer (IMO) to get really good.

Anyway, when I saw "waxbanks" at the top of the post, I figured it would be a thought-provoking one, and I wasn't disappointed.