I would think driving in the right lane is more dangerous on the freeway at least, because of onramps and offramps. I only drive in the left lane on a motorcycle.
Not to get too into the weeds, but depending on the stretch of road (frequency of onramps, and also the style), I might be one step to the left of the rightmost lane. Being in the leftward lanes isn't really an option at the speed limit, since I'd be blocking traffic, which has risks of its own.
It certainly feels safer. But I could imagine how it would be MUCH more dangerous. It's amazing how much difference even 10 MPH can make in an accident. Stopping distance increases by 25% between 60-70 mph. Keep in mind that the kinetic energy of your vehicle goes up with the square of the velocity. This makes braking much harder at high velocities. Not to mention the damage of a collision is increased accordingly. Surviving an accident at 70 is a lot less than 60.
Also risk to pedestrians goes up REALLY fast. At 30MPH a car has a 10% chance of killing a pedestrian. At 40MPH it's close to 50%.