As to AQA being easier, I do not know, I think it may actually depend on whether you are asking for the level of difficulty in the pure section, or the mechanics section or the stats section or any other section.
As far as I am concerned, I have only done Edexcel and from my point of view, since I have seen some AQA and OCR papers, I'd rather stick to Edexcel... I mean, I had a choice of taking either AQA or Edexcel at the beginning of the year, since I was almost going to teach myself, so basically Edexcel appealed more to me than AQA, probably the format of the exams and the wide variety of Mechanics modules which I like... Basically I would say the higher Edexcel Mechanics Modules are real killers, you won't want to do those if you're going for further Maths, however generally speaking C1-C4 is almost the same accross the few exam boards.