The Cgp revision guide are cheaper and are just as good as the textbook. So overall, Cgp.
If you are worried about missing any critical information, use the Cgp guides along with your specification.
The textbooks may be beneficial for you, if you really really want to understand a topic and practice it etc.
The Cgp guides themselves have very few practice questions and are mainly just facts you need to know.
This can be fixed by buying the practice workbooks or using past papers.