I would get the double lobe piercing but you should get whichever one you like better. Possibly you can get some small stick on earrings that just stick to you ear. Then you could try each version for a few days to help you make your choice.
I wish I could talk you into both. They make a great look together. If you are getting only one side done get the cartilage. If you are getting both sides get the lobes. Both are great piercings and you won't go wrong no matter what your pick.
I think double would look so much better. A cartilage will look alright but when you leave your hair down you cant see it but with double lobe you can so yeah. p.s have you ever considered triple lobe.
When I was in 5th grade, I thought the cartilage piercing was really cool, however now I think it's really kiddy and not very cute :/ Go with the double lobe piercing, it's much more cute and feminine looking. You can do really cool things like mixing and matching earring pieces. Personally, I don't like the cartilage thing. It's kind of awkward having 1 piece of earring all the way at the top of your ear where hardly anyone can see it. Anyway, choose what makes you happy, but I like the double lobe! :)