Frequency and strength. My issue with e.g. image classifiers is that when they’re wrong, they’re catastrophically wrong — they don’t misidentify a housecat as a puma, they misidentify a cat as an ostrich.
IE, "The only barrier to the software working perfectly is it's tendency to fail".
Which is to say this sort of argument effectively assumes, without proof, that are no structural barriers to improving neural network performance in the real world. The thing is, the slow progress on self-driving cars shows that reducing the "frequency of errors" can turn from a simple exercise in optimizing and pumping in more data to a decades long debug process.
I have a different opinion on this.
Humans don’t like uncertainty. We like to feel like our mental model of reality can predict future outcomes. When it doesn’t, we get very uneasy. It’s why we don’t like dealing with erratic humans.
Part of the problem with AI is it’s lack of interpretability. People aren’t going to want to interact with AI if they can’t intuit what it will do, even if you can show it’s statistically better. The performance barrier is going to be much higher than just a little better than humans. We don’t have that limitation when dealing with people because we can more easily infer their goals and actions.
Thinking that being a little better than humans is the threshold is a rational decision. But human trust is often irrational. The latter often drives politics which can regulate AI into a corner.
Also, on average is not a great target either, sometimes it makes sense, but there are plenty of examples where we definitely don't want more average work.
For example, see US Airways Flight 1549. Airbus had never tested a double engine failure in those exact circumstances so the flight crew disregarded some steps in the written checklist and improvised a new procedure. Would an AI have handled the emergency as well? Doubtful.
If don’t have good reasons to be confident that the error rate is stable, then you’re just guessing that you solved the problem, because it seems to work.