I think LA Noire is more "bankable" to turn out to be a quality title. Brink strikes me more and more as an experimental jumble of ideas that may or may not congeal into something formidable.
Normally, I'd ask whether or not you prefer online play vs. offline...but considering that you're torn on the decision, it would appear you appreciate both anyway. If you're worried about getting the most mileage, you're going to have to weigh Noire's campaign against the quality of Brink's online community. While I get that Brink is certainly designed for multiplayer, far too many games these days have a "two months and done" online community.
So, yeah.
LA Noire, in my opinion.