It's convenient print. The AMG site on the plus side is updated with new releases and reissues as they happen generally. While you would have to wait until whenever the next edition comes out. Another plus is the AMG site has all the different genres of music. So, you would not need to buy multiple books.
The reviews are exactly the same as in the books. Now the negative is that the AMG site is not as thorough in their proofreading. There are many mistakes on things like names, pictures and cover art.
A excellent book I would recommend is Geoff Dyer's book "But Beautiful”. It’s fiction but it’s excellent.
This site let's you see the changes between the 5th and 6th edition of the Penguin guide. There are no reviews just the rating changes and what was added or dropped.
Penguin Guide to Jazz Diffs: 5th vs. 6th Editions
The difference betwen the 4th and 5th Editon
Penguin Guide to Jazz Diffs: 4th vs. 5th Editions