The tune(s) you have sent pre-loaded on the flash tuner will be close to being correct for your particular vehicle, but a custom tune based on actual dyno information is necessary to get the maximum power your vehicle is capable of. A custom tune can be done locally or by e-mail, and requires dyno info along with datalogging results from either an XCal 2 or Predator. For typical custom tuning, neither flash tuner has a distinct advantage over the other; be aware that most people who give you advice on this are going to say the one they happen to have is better.