North End grabbed the victory thanks to Keith Keane's 82nd-minute winner after free-kick specialist Ryan Williams had cancelled out Joe Garner's opener.
"It was a good test against good opposition," Bentley told The Visitor.
"Preston are one of the top sides in their league and they brought all their squad here and made good changes.
"We knew it was going to be a tough task on a hot night but overall I thought there were some good signs there again. Stuff we worked on in training was evident in the performance.
"There's a bit of a concern over the two goals we conceded, certainly the first one when we had possession and they broke. That's when we looked at our most vulnerable, when we had the ball.
"It's a learning curve. We've identified it and we'll tidy it up. But I'm pleased that a lot of lads got 90 minutes under their belt and at this stage of pre-season that's really important.
"We scored a good free-kick through Ryan. Unfortunately we couldn't score one or two more which our efforts deserved but we did create chances and I'm sure the goals will come."