Originally Posted by Googleme
#2 seems like common sense but never thought of that sadly. Anyways im thinking ill just use the ebrake and never do that again because think about it, what situation can you think of that having the car in gear and the ebrake up will solve, but the ebrake alone wont?
I can't think of one and trust me since that day i've thought long and hard.
Over time and use, P-brake cables can stretch (you end up not applying as much brake as the handle position makes you think you are), or they can corrode, fray, and individual wires can break (the cable then unwinds as you pull on it, so it isn't as rigid, for the same end result as a stretched cable).
Engine compression braking (what leaving the car in gear relies on) is not subject to a similar level of deterioration until the motor is in such bad condition that you already know you need to get it rebuilt. You do want either 1st or reverse, as those gears give engine compression the best mechanical advantage. Other gears provide less braking effect, but are at least better than nothing.
Water can get inside the cable, and although it's probably an alien weather condition to SoCal residents, if it's below 32°F it then freezes and locks the cable in whatever position it was left in. And at least the early S107 Mustangs have a reputation for letting just this happen. Then you have a P-brake that you either can't use because it's "stuck off" or a car that you can't drive because it's "stuck applied". I'll take "stuck off" every time.
On an incline I wouldn't ever trust the P-brake alone and if it's steep enough I don't trust 1st/reverse by itself either. Awareness of conditions.