Seems like there definitely could be some power saving from not having to run radar. And I guess there could be some power saved in computing, since Pure Vision will (in theory) be less complex without having to overlay the radar data with the visual data. But I agree it would be pretty small.
There's a theory that the recent delivery delays on the M3s are due to a last-minute firmware update(s) needed, related to the new pure vision system.
Interesting update. As part of the removal of radar from the Tesla website, they also changed the list of standard safety features. The removed Automatic Emergency Braking (AEB) and Forward Collision Warning (FCW). Wonder how related to not using radar this is, and what they will be doing for existing cars.
They also added the interesting language "The following standard safety features will continue to be active on all new cars" that sure makes it sound like the removal of radar also removes some other features.
Before: Automatic Emergency Braking
Side Collision Warning
Front Collision Warning
Auto High Beams
After: Side Collision Warning
Obstacle Aware Acceleration
Blind Spot Monitoring
Lane Departure Avoidance
Emergency Lane Departure Avoidance
It is now all uniform data - camera feeds without radar - so it should be actually smoother and less prone to false braking as there I no need to reconcile 2 disparate sets of data into one cohesive representation.
Supposedly the x.4.15.x firmwares have vision-based FCW/AEB; my car is on the latest firmware in that chain and I feel like I'm seeing more false positives with FCW (and mine's set to late warning IIRC). Sometimes it's not even clear what triggered it.
These camera based adaptive cruise systems have been around for quite a while on other cars as I understand they are cheaper. For example, I had a Mini a few years back on which I had issues with the Adaptive Cruise Control. It deactivated in bad weather and when driving into a sunset (amongst other things). It couldn't be set above 75mph too. I suspected it had a faulty radar but after some research learnt it had "Camera Based ACC" and in the manual it mentioned the system was affected by bad weather, sun and other conditions.
I'd hope Tesla have improved on that system but the ongoing poor performance of the auto wipers since they switched to cameras for that doesn't inspire confidence!