There's no comparison between the two films except in the context of which one does one like better.

What I mean is that lots of people are comparing them as if they're two Westerns, which I think neither are, or two films that are similar, which I don't think they are, as if they're adapting the same novel or stylistically similar.

There Will Be Blood is comparatively loudly intense while No Country For Old Men is quietly intense.

The former, to use PT Anderson's words, is like a boxing match and has a Dracula-like protagonist. In my words (using movies that many have alluded to when talking about Blood), it's Raging Bull-The Shining-Giant-Citizen Kane-Treasure of the Sierra Madre hybrid which isn't implying that I think Blood is derivative or unoriginal. It's just shorthand, really, to allude to those films.

The latter is a contemplative apocalyptic "chase-thriller" film. It's a highly personal genre film worthy to be in the company of other exemplars of personal genre films like those of Hawks and Hitchcock.

I'm kind of surprised at myself because I tend to favor things that operate at No Country For Old Men's lower register, but There Will Be Blood is so mindblowing that my preferences were blown to smithereens.