For someone who does Higher Edexcel Maths, I would say you found that you got more scores in the Edexcel Maths because the standards for the grades are lower as the questions are harder whereas in AQA, the standards are higher but the questions are more specific so it's harder to get the questions right and gain marks. Also, in Edexcel, most questions are based on the basics but just layered up so maybe that is why. Edexcel is hard but it's easy to gain marks as your working out can get you a few marks even if you got the answer wrong and AQA is really specific with the working out and answer. However, it could be that since you re-sit your exams, you knew the type of question that could come up or you may have practised more on the ones that you knew had to improve or the paper was a lot easier, to begin with?
You should definitely see the specification to see where you may be lacking or how different the specifications are from each other.
Hope it helps! (:
Don't worry over time, everything will get easier! Congrats on passing by the way. Keep on working hard! (: