Proper parking brakes, even those old 60s things, hold very well on fairly steep grades..... it is a law thing. If they don't, fix the problem.
I might be an old geezer, but electric motor operated parking brakes are just one more modern device that can fail and leave you stranded. Think what might happen if they won't release. How would you make them release if there were a motor or gear drive failure.... take off the wheel, huh?
I would seek a better leverage advantage if I were too sickly to pull a manual type parking brake.
