Body cams are a little bit more specific to "actual interactions with police", and I think it's worthwhile for both the officer and the private citizen to have access to that footage.
LPRs is interesting because this falls kinda in a "right to be forgotten" territory. The car "saw" you, in a public space, and we're recognizing that it's really not okay for police to remember everywhere they've seen a car. As an RTBF supporter, I'm alright with that. They arguably still can have a lot of value to police, if only able to record plates of cars of interest. Since an officer can't read every plate on the road, much less compare it to a list, an LPR can look for plates from BOLOs or open cases automatically, presumably, and notify the officer if it sees one, without hoovering up and storing every plate it sees.
But there's also a lot of interesting value in being able to track someone's location during an investigation, even for exculpatory reasons. I do track my own car, and the police could issue a warrant for that data, though they'd have to serve it to me directly. Perhaps onboard black boxes is more the direction this should be heading. (Most non-base model cars likely have GPS already and probably record their history already, mind you.)