Freddie Sears's fourth goal in five games was enough to give the U's victory over the Lilywhites, who had defender Bailey Wright sent off near the end.
Dunne said: "It was a very good victory. There are all kinds of victory, but the manner of our victory was very, very pleasing.
"It was a gritty game and it was a game where discipline was key.
"I thought that we had enough quality in terms of how we attacked Preston to win the game. We played the first half well and we hit the post and got into some good situations.
"Preston threw everything at us and we defended exceptionally well and knew what was coming.
"There was a good firm base from which to attack with and when we got opportunities, I thought we would take them.
"The first goal has been key over a lot of the games we've been involved in and I think once we scored it, you could see the confidence lift.
"We have good quality, attacking players and we're a threat."