depends on who is driving... and how steep the slope... the one outside Mt E, no matter wat car u drive, if u dun pull hand brake, then press accelerator and release hand brake, your car sure roll backwards.
i always put to N whenever possible. when in D, the clutch is always engaged and will keep wearing your clutch plates. furthermore if you're the kind who always go fo red light sprints, it'll wear your clutch out pretty fast. On average, a new set of clutch plates should last you between 3 and 5 years for normal drivers.
For chiongsters or PG regulars, 1 year or less is also possible
Forgot to add, I drive manual most of the time now. I prefer the ablity to control my engine braking during turns.