Need help choosing between 2 women!!!! Seriously!!!?

Was engaged to a girl who was 25 four years ago. She cheated on me with a co-worker and we broke up. She came back begging to take her back two months later. Typical stuff, "Was stupid, didn't know what I had, etc". We got back together and it's been fine since but I never completely got over the betrayal. Now two years later I've met a girl that I have grown attracted to, we have the same likes, and I'M the one having an affair but don't know if I want to let go of the attachment I've grown to have with my girlfriend to go with this new girl I've been seeing for 7 months. I'm 37 and they are both 31 so I don't think it's a stupid age thing. I feel like I don't have the baggage with the new girl (or chip on shoulder) but I do have an attachment with the girl I've stuck with over the years. Any insights folks?