I went with WDADU/I&W because Kevin Moore
No, but seriously, those two albums (especially I&W) have some of the most amazing music ever written, imo
That's not to say there is anything bad about ADTOE/DT12 - Both are definitely very good releases. I prefer ADTOE in terms of songwriting, and I prefer DT12 in terms of the sonic presentation.
Now that I think about it more, I think nostalgia is a big factor in my opinion of these two pairs of discs.
"Images & Words" is literally the album that introduced me to progressive metal. Oh sure, I had dabbled a bit prior to that (Deep Purple, Fates Warning, Queensryche, etc) but I never thought of myself as a "prog fan"
But when I&W finally clicked, my entire concept of music shifted gears in a big way.