Hey FastCar,
Personally I would recommend the CGP guides, one because they're cheaper and two because (oddly) the information seems to be more reliable. I have a CGP book and an AQA approved study guide for 9-1 Geography, but I noticed that some of the information in the AQA approved book was for the old exam and not the new exam, hence I decided to e-mail AQA to see why this was. They replied stating that different books have a different way of presenting the course so they may include information that the exam board doesn't expect you to know for the exam. The CGP books seem to be more reliable because they solely look at the specification for the information they need to include, so you won't have to learn anything you don't need to. I have been studying from the CGP book and I've put the AQA approved study guide to one side for the moment.
However, I would like to give the benefit of the doubt and that was just an exception, but also if you don't like the style of the CGP books (as some people don't), I would use the AQA approved books. Just as a little add-on, I wouldn't buy the study guides from CGP, because I bought 3 for Chemistry, Physics and Biology yet I bought the revision guides for each of them as well, and they essentially had the same information except one was £18.99 and one was £5.99! You should also buy the exam workbooks available from CGP, I'm finding them extremely useful.
Good luck for the future!
~ Xez