I've extensively used coated blades from Benchmade, Spyderco and Emerson.
Spyderco's DLC is, by far, the best. It often looks "scratched" after use, but what I'm seeing is pieces of whatever I've cut embedded in the DLC, the blade wipes clean and looks new. The only thing that ever wore the DLC off was when I used the blade to pry some heavy staples out of wood.
Emerson's black ceramic coating is pretty good, just not as awesome as Spyderco's.
Benchmades, I don't know what it's called so I'll go with "Black Magic Marker" coating shows wear from cutting cardboard. That said, I don't mind, I think that the 'wear' makes it look cool.
If you don't like a worn look in a coated knife, do not buy a coated Benchmade (unless it's the HK14715, it's an epic knife that only comes in coated D2).
Ironically the cheapest one I own, a discontinued BM HK Ascender has shown the best wear resistance on the coating of any knife I've owned. From looking at it you wouldn't believe how much use this knife has seen.
It's my dedicated "Cardboard Box" cutter for years and the coating has held very well I think.
Beautiful polished edge!
They must have changed something, my recent black Benchmade wore surprisingly easily.