Boxes:
Balance = easier, but if you start slipping off to one side its harder to save yourself
Stickiness = generally stickier
Trickability = easier to do spins onto the box, harder to do spins off because you have to grip the correct side off box almost as soon as you get on
*boxes may or may not have coping which can greatly change things
*stickiness of box depends greatly on the hill and conditions, some boxes are slick AF, and others not.
PVC:
Balance = harder, but locking on is easier
Stickiness = Rarely, if ever, sticky
Trickability = spins on are a bit harder to balance, but tricks are generally easier to do on pvc