This is hard to answer, and I probably won't vote in the poll just yet. Strange as it seems, I haven't thought about it.
It's quite clear to me that post-SFaM, I prefer their "prog" stuff. Octavarium is my favorite recent album. I like about half of SDoIT (like, not love), and I consider ADToE a return to form in large part because it emphasizes the prog elements. The song Octavarium might be the best thing modern Dream Theater has done.
By contrast, I can't stand a lot of their recent metal stuff. Train of Thought, Systematic Chaos, BCSL...this all sounds like a mid-life crisis in music form.
But really, when Dream Theater was at its best, the prog and metal were inseparable. Songs like A Fortune in Lies, Under a Glass Moon, Voices, New Millennium, and Home are not straightforward prog songs, though they may emphasize the prog over the metal just a bit. It's the combination of elements that works, and with the exception of Home, I wouldn't change these songs one bit. They're beautiful, awesome compositions.
So my answer varies depending on the era. The sort of metal Dream Theater gravitates toward now does absolutely nothing for me, and it's pretty different than what you found in Under a Glass Moon. The sort of metal Dream Theater plays now gravitates towards "headbanging" and maybe "jamming," but not much else worthwhile. There's no beauty or grace in it from what I can tell. The metal they played earlier? Loved it.
As for rock/pop, they're fine. Octavarium and Falling into Infinity place more of an emphasis on them than most DT albums, and they're both great. Some of their accessible rock and pop songs, like Another Day, stand tall with their long, complex compositions.
In any case I'd much rather listen to Status Seeker than Constant Motion.
I may vote for Pop/Prog, because they're the most consistently decent, at least. I'll still have to think about it.
EDIT: I have heard, even from metalheads, that DT's not that hot of a metal band. Might point toward prog being the priority, because to be honest I really do think they aren't that great at the type of metal they chose to zero in on recently.