Just my 2 cents, but both of Paul's ending sucked.
Good ending: as U mentioned at first Paul was a romantic guy and really cared about Jen (the main motivation for the cheating) but in the end he treats Jen only as a cocksucking whore. It's written in his thoughts about Jen in the ending. To make things worse the narrative tells us "he always wanted to fuck Jennifer all over Mark's stuff", and the fact that he's bangin' Jen is just some kind of childish victory over Mark. So from a good guy to a capital asshole in a blink of an eye. shitty writing imho.
Bad ending: Mark breaks up with Jen and she puts the blame on Paul. But why the fuck? She cheated on her bf willingly there was no blackmail or forced stuff in this route. Even when P shows his support Jen only acts like a bitch and plays the victim....
Only good (NTR) route is Laurie's(best support character) in my opinion. It's almost well written. My only issue with this route is that Laurie was a total whore before she met Jen. So her transition from a slut to a loyal gf happens a bit too sudden. I think L's character arc could be executed better.
And yeah the strapon chick was Kelly, in the newest version that scene happens only if you made Jen spy on her earlier at the park. ("fortunately" the writer fucked up this one as well, because later in Paul's elevator scene, Jen refers to the trash chute affair even if it did not happen)
I think Laurie fell in love. That's what makes the difference. From the very start, her and Jenn have instant chemistry. And Laurie starts taking her schoolwork seriously in an attempt to impress Jenn. And it works, because Jenn realises that Laurie isn't the dumb bimbo everyone seems to think she is, but is actually one of the smartest students in the school. And someone she could seriously have a relationship with.
So maybe it is a rapid transformation. But she has a big incentive to change. Namely to impress her teacher, who she's totally fallen for.
I think before she met Jenn, Laurie didn't really care about anything, her life was all about having fun and if she'd never met Jenn, she probably would never have gone to college, and would have ended up more or less like Kelly.
I think you're right. That was definitely the best part of the game, and probably one of only two routes, where Jenn ends up genuinely happy.
But the ending was still pretty short and rushed, and I think that was the problem for pretty much all the routes, except Jimmy's and the gangbang ending, which the Dev seems to have invested most of his effort in to. I think he invested as little effort as possible to the other routes, and just wanted them over as soon as possible. Which is why Paul's endings were so disappointing ( he completely lost interest in this route ).
Fortunately, with Laurie's route, we'd already had some great scenes between the two of them, and after the last of these, Jenn dumps Mark anyway, so it was pretty obvious where her and Laurie were heading at that point. And whilst I think the actual ending for them was too short and trivial, it was still just about enough to bring a reasonable conclusion to their storyline.