They don't seem to be quite as sharp out of the box, but last much longer.
They can be sharpened, you need a fine-grained diamond or silicon carbide wheel. I don't know if your burr is fine enough.
Carbide is brittle compared to steel, so the sharpening angle is less keen. Steel can be sharpened to a finer angle because it is tougher. If carbide is sharpened to the same angle, it will just chip off at the edge in short order. But carbide is much harder so it will hold it's edge much longer and is particularly useful in dirty wood that will quickly dull a steel cutter, such as cutting off the stump near ground level or where I suspect there is metal buried somewhere inside the trunk like along an old fence line.
In my day job, we use carbide chains in our roof saws, cutting ventilation holes right through shingles, nails, flashing etc. A steel chain won't last a minute in that application.
