You'd have to look at the Spec and past papers. I doubt the content could be different (it isn't between exam boards as the requirements from the government have been tightened) but possibly the way the questions are phrased are different. Look at some past papers.
You can swap boards for AS to A2 so no issue there - depends on what your school/college/examcentre offer.
I have some old MEI books and some old Edexcel books. MEI are much more discursive and talk about where ideas come from and where they go (with little historical anecdotes) whereas the Edexcel books are much more functional (four bullet points of ideas, three examples, some questions). YMMV.