I gave both the relevant albums (probably my 2 favourites by the band) a full listen tonight, and these 2 tracks stood out. It also seemed to me that these songs have a lot of things in common. Both fall into the middle of some kind of bigger conceptual picture (A Mind Beside Itself, Scenes From A Memory), they have a vaguely similar structure, both build to a guitar solo of stunning virtuosity, and they're of almost identical length.
There are a dozen things which make Dream Theater one of my favourite bands, and both these tracks contain most of those things. There's so much skill and technique combined with great taste and beauty. Both tracks have soaring choruses. There's a lot of breathing space in these songs (more so in Voices; Beyond This Life is one of their 'busiest' tunes). From Voices - the slow build-up to Petrucci's histrionics is perfectly measured, and to my ears they haven't quite captured that sense of suspense since. In Beyond This Life, the unison is one of their greatest moments, and what a brilliant culmination to the instrumental section, a mad flurry of ideas composed in the white heat of inspiration. They revisted this kind of music in Outcry, my favourite song from the last 2 albums, and no band does this kind of thing better. Sometimes (rarely, I should better say) it can feel a bit forced when they compose those long instrumental parts, but more often than not it's an exhilirating journey. Beyond This Life is some of their best work in this area.
So although I've made a poll out of this (and Beyond This Life gets my vote in it), I'm really more interested to hear opinions on these 2 tracks, which one (if either) affects you more and why.