It depends on the subject and the teaching being offered. In EDEXCEL exams the questions are clearer and easier to interpret. For AQA the wording is heavier and more complex. If you are bright you don't need to worry really. It used to be the case that EDEXCEL qualifications were not valued as much as AQA but I’m not sure if that is still the case. Collages and Universities look for at least 5 A*-C and some schools can ask for 8 A*-C regardless of the exam board.