Killing Them Softly has the very idea of Pulp Fiction behind it: people involved in crimes are real people too, not just criminals. The result is slice of life of those people.
The difference lies in the way it is presented. KTS is less comedic than PF, it has laughs, but not that surreal effect that comes close to caricature. It is a more realistic version without all the flowery prose, with more in your face camera moves, instead of the odd, yet effective, choices that Tarantino makes.
Pitt is excellent, and I like his choice of tone. A very mature Brad, letting us know he can do things in a more muted format.
Violence is there of course, the rhythm is very casual, the story interesting, and the bits of action gripping.
Very effective movie. I highly recommend, unless you can stand that kind of violence. The only reason I didn't give it a perfect mark was the fact that being a very brutal film, I won't able to watch it as often as my favorites.
See it, well worth it. The theatre will bring an addition dimension, but it that's my point of view.