Girls, which one should I go for?

Ok so I liked this girl whose a grade younger then me. I did not know her til last week when a bunch of families went on a vacation together. We got to know each other really well. I knew at the time she was seriously talking to someone and they both liked each other so I did not make any moves. I did notice though she was being flirty with me. She is not a slut but I have heard she is flirty with some guys. Three days ago after I left the vacation home I found out that guy hooked up with two girls at a party. So I tex to her and asked her how she was, we had a good conversation until I had to go. I thought this was my shot but I talked to one of her best friends and she said she had forgiven the guy. So I talked to one of my really good girl friends and tell her about it. She told me to text her and talk to her. I wasn't in the mood to talk to her but today she sent me a text and we had another good conversation. Now the really good girl friend I've been having a very small on and off crush with her since freshmen year. She used to have the biggest crush on me freshmen and sophmore year but I was always afraid to ask her out. She made it sound like she liked me too and all my friends tell me she has feelings for me. The only thing is she has the reputation of a slut. Now the other girl is definetly cuter but my friend is still pretty cute herself. So what should I do? Should I chase after the girl I've fallen for and think is beautiful or be with the girl I know I can date and grow feelings for. Now the girl who is a somewhat of a slut hooked up with 13 guys at a halloween party, yes 13. She was drunk but that's what I'm afraid of her drinking and cheating on me. The prettier girl is somewhat prude I think and I am completely fine with that, I'm not looking for now anyways being a junior in high school. That's just a little added info that i didnt post last time