So I have two M3s, one from 2018 on the FSD beta and one from 2019 not on beta (mine and my wife's), and I've driven them both extensively to and from work. If it is really the case that the beta build disables my 18's radar, then I can say for certain that beta brain is better at highway driving than non-beta + radar brain. There ARE differences for sure. The beta stack can perform interchange maneuvers that non-beta can't. It also reacts to traffic better. Also, for what it's worth, on my 23 mile commute, I get approximately zero phantom brakes that aren't due to the highway speed limit changing. (That is to say, both cars hard brake when the 65mph limit goes down to 50 suddenly, but I'm not sure this is really phantom braking, but instead just following the law.)