In a best case scenario, I'd think that sensors would have the advantage of perfect clarity on when they are working, and when they aren't. Eg, if a stretch of sensors goes bad, cars would encounter them and immediately attempt to safely stop, pull over, etc.

With this, we have AI having to predict when it does and when it doesn't know where the road is. A sensor approach could be akin to a railway, and the rails are either detected or not.

A merge of the two methods would still be needed of course, to detect obstructions in the roadway, navigate safely in the emergency event that no sensors are available, etc.

It would also be cool because we could define when and where those new roads are available. You wouldn't be able to drive AI to the Oregon Coast and have it suddenly fail on an untested cliffside. The road is either AI friendly or not.

I'm sure there's flaws in this line of thought, I'm merely speculating.