In my opinion the interstates are much safer. I've had more close calls on secondary roads. Cars pulling out from driveways or side roads, passing farm equipment, people who aren't sure where they are going stopping or turning suddenly...etc.
Yes the interstates can be boring but most of them follow or replaced what was once a heavily traveled secondary road.
If I have the time I would often travel secondary roads to see the sights but I would be a lot more alert than if I was on the interstate plus I would stay at or below the speed limit for a safety cushion.
