I agree with jokerboss. As i dont really like to farm i bought fly. But if you like farming ext + is the way to go it can also make a bit of money on the side. If you want to get around the map faster and be able to build easier in both the main world and the aither then get fly. Good luck deciding!
Good luck! And if your getting another user to purchase it for you, remember to take screenshots and make sure they are trusted! Have fun, fly is amazing!