How good/durable is a Campy threadless headset, compared to other aftermarket headsets (king, etc)

I have the Campy threadless non-integrated. I works wonderfully, it is smooth and buttery like you would expect from a Campy product. My one problem is that it has a little rubber gasket on the outside to cover up the holes that are used to inject grease without disassembling the headset. The rubber gasket broke, I didn't notice and I rode like that for a while. The headset needed overhauled, but no big or expensive deal.

I have never ridden King or other headsets, that are non-integrated but I would assume King at least has equal performance with less maintenance.

My advice is if you are riding Campy components stick to the campy headset, if you ride shimano then go with another brand.

Get a King, install it and forget about, regardless of what components you have!