I have a number of modern arms with Duracoat and Cerakote. They're really different from bluing- as someone already said, more black. Bluing with Laurel Mountain Forge results in a black too, but from those I've seen more of a "polish" like hot-dip bluing, even if it's black. The two paint-ons are lots more dull.
Haven't seen a brown version of either brush-on. But there's such a wide range of "browning" results out there using other methods, it might fall somewhere in the realm. I know I strongly dislike plum browning for example, while the unique browning solution/process used by GRRW produces the nicest brown I've seen. Quite tough in addition to buttery texture almost, if I can use that word.
Speculation here, but I'd really have to see the brown version of Duracoat before I could react to it. Guys point out that it's "just a spray." There's an up side to that, even if it's not as tough as conventional browning: If you scrape it up, just touch it up with more spray.
Anyone has photos of the Duracoat brown, I'd sure love to see them.