I have probably rented cars about 200 times in my life. I have not ever had a dispute about damage (knock on wood). I think taking photos might give you peace of mind. I always do a walk around and only note items that are more significant than scratches or scuff marks. Sometimes the cars are wet or are in a dark garage, which makes it harder to view any previous damage.
When I return the car, the check-in person usually does a brief walk around but they seem to be looking for dents and not scratches.
Good luck!