Systematic Chaos for me. I'm one of the few who thinks the album is very good, and that has some amazing musical moments. ITPOE has some of my favorite moments from all DT history. The instrumental sections through the album are very technical and fun to listen to. The tone and mix are great, every instrument sounds great, James sounds great and MP's vocals aren't as annoying as in Black Clouds
The only song I don't like from it is POW, the rest is pretty solid.
Black Clouds just doesn't make it for me. TCOT is also one of my favorite DT songs, but the rest of the album just sounds out of place. ANTR is great, but the final section (the one with all the changes and the blast beat) is long for the sake of being long. Same happens with TBOT, which, apart from the cool Rush intro and THAT solo, the rest feels forced because they wanted to fit all of MP's lyrics there and just made the song longer and longer.
With the exception of a couple spots on the album, MP's vocals really suck. (ROOOOAAAAAAAARRRRRRERGGGHHHHHHHHHHHHH)
AROP has a great solo section, but the rest of the song is just weird.
So, SC is much better, at least for me.