eh, a bunch of people are gonna bash them because they're not metal but seem to like thinking they are, but whatever, they're just music, and very good at it.
Erotomania & Dance of Eternity, I second those for being complex, hard to play songs, but that's not why I like the band.
I'm fond of the solo in The Mirror, seems difficult to pull off, an it's in a very good song (one of their more metal ones.. That and Lie are a tremendous combo). And Scarred... The solo in that is fucking godly, can't get enough, but it's in an average song.
Portnoy,well you can hear his prowess in just about every song. Overture 1928, Beyond this Life are good examples of that.
But for whole band performances... Well there's usually atleast one stand out member in every song, can't go wrong.