What's a PRS?
If it's some form of tow/haul mode, I prefer that for downhills but I am watching and ready to help it along into a lower gear before speed gets out of hand. Uphill, I don't find it much of a difference so usually it's just left on.
On quick up and downs, I try to feather the throttle (assuming I'm not disrupting traffic) so as to minimize gear changes. So on an uphill, I will try to give it as much gas as I can but not enough to force a downshift even if I bleed off 5-10mph. Then I let it pick the speed back up on the downhill.