I have both. The Didache Bible is a much better value in my opinion. Make sure you get the RSV2CE edition if this is the one you go with. It costs around $40-$45 and has great footnotes based on the Catechism, along with around 100 “special topics” sections which typically more thoroughly connect Scripture to the Catechism. Each book of the Bible has an introduction in the Didache, although they are just one page long. It is hardcover and good quality.
The Great Adventure Bible will cost you about $60. It is good quality and has more colorful pages than the Didache. However, quite disappointingly, there are no book introductions, which I think is a huge omission considering how expensive it is. Its focus is more on “Salvation history,” i.e. providing you a type of “study journey” on how the Old and New Testaments connect, the story of God beginning with our first parents and leading to the foundation of the Church. In contrast, the emphasis of the Didache is on providing the Scripture and Tradition basis for Church teachings.
Ultimately, it depends on what your area of interest is - the “historical” aspect of Scripture or the “doctrinal and moral” side of it. In considering price, I think that the Great Adventure Bible was marketed to go along with the whole “Great Adventure” study timeline and series, and I’m not sure how much that costs.
Anyway, in summary, my vote goes to the Didache. But again, each of these Bibles has a very focused area of specialization: Adventure = history, Didache = teachings.
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