Perhaps there are instances where radar cars have less phantom braking, but it is far from empirically establish to be factual that a majority do. I, for one, for reasons stated previously, prefer the vision approach and have extensive use with both methods.
If you really believe there is no way to see, with vision, in front of the car in front of you, then I'm not sure what to say. Using my own two eyes I can see vehicles in front of the vehicle I'm behind very easily, I'm not sure why a camera couldn't. Furthermore, I suppose the display in the car could be lying but I'm not sure I understand what the benefit of that would be.
Less phantom braking is unproven, better emergency braking is unproven, but I 100% agree that I'd like to have the higher AP speed limit back. That is the only downside to Vision that I have experienced (but it's likely saved me money in tickets). For the record, that is with about 10,000 miles that I've been in Beta and using Vision only. Plus I have a Y with Vision that works perfectly fine with almost zero phantom braking.