The correct size will depend on your personal preference. The 4 door jeep is quite spacious. This will be quite an advantage for you and your friends. The performance of the 4 door Jeep is also good. The advantage of the 2 door jeep is that it has an overall good appearance which would be trendy for a 15 year old.
Since when does a 15 yr. old have a Jeep? Or a car? In fact, I don't believe that you can get it registered until you are 18 unless an adult does it in their name. At 15 in most states, you can't get a license, so who's gonna drive it? All else being equal, get the 2 dr.