Are integrated headsets inferior?

I don't think so. I'm talking here of fully integrated headsets, where the bearings drop directly into the head tube with no pressed cups to sit in.

In 2002, Chris King published an article called Integrated Headsets Explained which vigorously attacked these kinds of headsets. In his view, they were a flawed design. Note however, that his firm were not producing any, so a cynic might say that he was attacking a competing product type. There was a hot debate about them in the years that followed, for example here. Many took Chris King's side and I can understand that, because his products are lovely and he clearly knows a thing or two about headsets. However, many did not agree with him. At that time, I stayed on the fence, not really knowing who to believe, but more importantly, looking for evidence supporting either side's arguments.

Since then, I've used integrated headsets a lot. After riding them for some years, I've no issues to report. On the contrary, the ease of fitting, smooth running replaceable angular contact bearings, and the clean finish are all superb benefits. Indeed, nowadays, many top notch frames are designed to take them, Colnago, Hope, Cane Creek, FSA, Ritchey and other great bike brands make them.

Most importantly to me, I haven't found any evidence that proves Chris King's allegations against the integrated headset design. In my opinion, for any kind of headset, what really matters, is how well it is fitted, adjusted and maintained.