Hey, just been learning this type of movement myself (still new to robots in general).
Linear motion is a calculated straight-line path, therefore it is always known and repeatable. PTP is "fastest route" which usually involves curved paths. There is no guarantee of the path taken for a given movement.
PTP can be safe if you know the area of movement is clear, but linear is still safer since you know exactly where it's going and how it's getting there.