Ugh, you had to answer a tough question, didn't you? :-P
Spring '77 is definitely up there, especially early May at Barton Hall. Also really enjoy 1983, Brent really started to come into his own & inject his own flavor to the mix. Pretty much any tour in '74, the Wall-of-Sound really adds a dimension that's quite unique.
Those are my top-3, in no particular order.
Disclaimer: I'm often wrong. :-P