I wish I could answer your question for you. Even if I could, I would not do that because doing so would make me responsible for your choice.
What I can do is give you some questions to ask yourself: Why, for example, is it important to make a choice at this point in your life? You are only 21. You have limited experience relating to men. You’ve only known the new guy 6 months. I encourage you to make more male friends, to date a number of men, and to gain more wisdom about what you need in a relationship before settling down.
Regarding the former love: Please remember you were only 16 when you were together. Your needs as a young adult may be different from what you needed or wanted as a teen. It’s unusual for a first love to be a permanent one (although it does happen). Ask yourself if you would be interested in him if you met him for the first time now.
Your friends’ opinions are important but shouldn’t be a deciding factor. You will be living with the consequences of your choice every day — not your friends.
It is not unusual for a person to bad-mouth an ex in the wake of a break-up. I suspect your friends all know that. If you do decide to go back to your ex, explain to your friends that you said things in anger that are no longer true. They will probably understand.
However, sometimes our friends can see something we can’t when we are emotionally involved. Do take their counsel seriously if they have serious concerns.
Almost everyone has a “what if” guy. What if I had stayed with him? What if he has changed? What if he was “the one” (something, by the way, I simply don’t believe in). What if, what if, what it. At some point, a person has to decide whether to try it out and see or come to terms with the reality that whatever that person offered was for that point in time in life, not for the present.
If you continue to see your present guy but keep up the “what ifs” about the ex, it may be a way to prevent yourself from committing too fast. That might be a good thing for a while. You’ve only known him for 6 months. But if you keep it up for too long, you may be preventing yourself from committing to a quality guy. Only you can make that decision.
I hope this gives you some things to think about.
I wish you well.