The methods are all the same. They all come down to did not arrive or missing item in the box. But some refunders say details which make them sound more reliable and get the refund straight away, but, I think this is rare.
Finding a good refunder is like a lottery. Find someone who has positive reviews for the store you need and also contact them to make sure they can do it. If they fail, it's most likely something to do with your acount. Either you've refunded before or the courier recognizes the address and refuse the refund, etc. The refunder always uses the same method, so if it fails, the fault is not all his, but still sucks to fail because your chances of getting another refund drastically lower.