Relationship troubles can always be boiled down to immaturity. The nice thing is that as you get older, you get more mature and so better at navigating the various things that blow them up.
For your specific situation, I’d sit down and meditate for a bit and let your gut tell you which relationship to pursue. Once you’ve decided on which one to go for, devote 100% of your time to her, assuming she wants to be your girlfriend of course.
Me personally, I’d go for the one who didn’t cheat on you. Nobody changes just because they got caught or owned up to cheating. Owning up doesn’t change the reasons you cheated.