Go with your heart. Which one makes you more happy? Which guy has the same goals and dreams for their future? It's a tough decision esp if they are both nice guys but just make sure you have things in common and it's somebody you are compatible with. Good luck and may the best man win.
How about starting by just being yourself for who you are! Also, your playing with fire and be very careful that the one who might get burned is you and end up alone. Never, play with someone's feelings, because I believe in Karma and you just might lose them both, so decide. Which one treat's you with respect and dignity. Which one do you enjoy being with the most? Which one does your heart and conscience tell you to be with.
Also, you might just not be ready for a committed exclusive relationship and you need to tell begin to be honest and tell them both. In that case, tell them both that at this time, you are not ready for commitment exclusive relationship, but would like to date and be non exclusive, until you feel you are able to commit to the right man.
Unless hook up means something different here then I would say forget about them both. Hooking up means they are only interested in having sex. If you mean they both want to go out on a date then go out with both of them. Tell them both the truth that you aren't exclusive, that you are dating around and see which one you like more. Over time you will get to know both of them better and you will be able to decide who is the one for you.