I'm in the habit of using my parking brake in addition to the park lock. Someone told me years ago that it would help save wear and tear on your transmission as the parking brake will hold the weight of your vehicle and keep it from moving rather than putting all that pressure on the trans. I don't know if that is true or not, but it has stuck ever since. However, if my car is going to be sitting unused for an extended period of time, I will not use the parking brake. I will park on a level surface and only use the park lock. The reason for this is an experience I had last year when trying to sell one of my ICE vehicles. We had purchased our minivan and were trying to sell our Hyundai Tucson. Since we were driving the minivan all the time and I wanted to keep the Tuscon nice and clean, I parked the Tucson in the street, engaged the parking brake, and it sat there for a about a month, maybe a little longer, before it was driven again. Once we had a buyer, I wanted to take the Tuscon out to get it one last clean and vacuum so it was all nice and pretty for its new owner. I started her up, disengaged the parking brake, and put it in drive. When I pressed on the gas, the car wouldn't budge. After several attempts, the car started to move slowly but the rear wheels were seized up. With the parking brake engaged for an extended period of time, it had gotten stuck in the lock position. It took several cycles of engaging/disengaging the parking brake and then one final stomp on the gas to break the wheels free. Ever since then, I will not use the parking brake if a car is going to sit unused for a long time.
EV: 2012 Mitsubishi i-MiEV SE, Raspberry Metallic, Premium Package - Purchased 07/11/13
PHEV: 2017 Chrysler Pacifica eHybrid, Bright White, Platinum Package - Purchased 05/01/17