BEST concert(s) you've seen?

Musically, I don't think they have all that much in common, other than an improvisational approach with a dose of psychadelia. Lot's of cultural similarities. But musically, the Dead were based in R&B and bluegrass, with a signature basic jam pattern of going up and down the tetratonic scale.

Phish is much more jazz and rock based, with some ska, and funk, a lot more hyperactive sound at least in their mid 90s period, and they have a much tighter sound. Sound wise, they are much more akin to Zappa. And their earlier jam warhorses were actually fairly structured, sort of a danceable version of Crimson. Their more recent offerings of songs with shorter "composed" sections offer more openended jams, which is at least one cue they took from the Dead.