This guy flirts with every girl, but he asked me out... serious or just playin?

Want my honest opinion? I think they are BOTH players, and they have a competition going to see who can score with you first! This may seem flattering to you, but be realistic...you will never be able to trust either one of them. The fact that you have resisted them so far is making them both turn up the pressure on you. Don't be surprised if they have a little secret bet between them on who will get through to you. This is not what you want from a bf, believe me.