I'm curious about the major difference between the two.

PF vs DF

As I understand it, duty finder and the roulette pushes you into a guildhest with others randomly (around same level) and you just go do the mission.

With PF does it find a group and then everyone has to run to the location of the quest, or will it also push you into the instance with a group of people?

Am I misunderstanding it altogether? I'm new =)