I love both albums to death, but I'd say Wish You Were Here. Shine On You Crazy Diamond is one of my favourite songs of all time, and Welcome to the Machine and Have A Cigar are somewhere up there as well. But it's important I mention that Images isn't my favourite DT album, and that I'd rather listen through Images on a given day than WYWH. The latter is musically better, but the former is probably more entertaining.