Protect my vehicle when it is most vulnerable - any time it is parked - other than in the home garage.
Most insurers have largish deductibles - mine has a minimum deductible of $600.
That can end up in a very expensive shopping trip - or doctor's surgery visit in our case.
Happened to our 3 year old car recently and avoiding a repeat was the primary reason for the purchase of a 2ch dash cam.
The criteria was number plate recognition - at which I felt the 4K Blackvue was superior.
Of course that it a matter of opinion.
But no point purchasing any dash cam if the number plate recognition is not right up there - for that I believe 4k is essential.
Other bells and whistles - GPS, speed , red-light cameras I have had on my Garmin car GPS for years - are expensive add-ons.
In any event the main focus should be on the road ahead - in fact on 100 metres ahead - not on some fancy in-car kit.
If an accident/incident happens it goes to a special folder you can review at home with a calming scotch in hand whilst you plan your revenge against the jerk that caused it.
With the best unchallengeable witness evidence possible - camera footage.