It's very hard to pick one or the other. You also would have to consider them. They are friends? It is a really tough situation. Trust me I have been there and still am. I know it is not somethind attentional and that it can just happen.
I have been with my boyfriend now for about 5 monthes. I love our relationship. We are there for each other. We are in no hurry to move in together. We want to take our time with our relationship. Let me also include that I'm 26 and he is 31. I met Robert through my ex. Both of them have been friends since they were 8. Trust me I did not want to ruin their friendship. I'm glad that they are still friends. My ex knows that he wasn't there for me and very selfish about many things. He also knows that both Robert and I are very happy together. My ex talks to both of us. He is friends with the both of us and has excepted our relationship. It is hard because at the beginning of Robert and my relationship my ex fought to point out our inperfections. Both Robert and I agreed not to talk to him for a bit. Now I can have a conversation with my ex without him saying anything bad about Robert. The same goes for Robert. It's nice that we can all get along with each other.
Trust me it is hard, but it is your choice on what makes you happy. You are still young so take your time. You don't want to jump into something you will regret.