Been to more Panic shows than I can count. I went to my first Phish show several months ago and I was impressed with the crowd. I think I had always been led to believe it would be super dirty people but it wasn't at all.
I'll take the Grateful Dead over anyone anytime. I have 60 shows I got on cassette tape mailed to me by some other deadhead on a forum. He had transferred them to CD and pains S&H to mail them to me, a 15 year old realizing that improvisation in music was the absolute best part about music. I still have those and countless other shows I put on CD and on my mp3.
I make a point of listening to at least one set every day; and it is just never the same.
I'm going to include Yonder Mountain in this conversation as my second favorite jam band. Their show at the Varsity was incredible for a guy who had been a fan for 7 years.