@curiousjim
Personally, I found it easier to develop a sense of how my tastes related to the Penguin Guide ratings because there were only two reviewers who wrote them, jointly. Due to the greater number of reviewers contributing to the All Music Guide, I found this harder to accomplish but perhaps others will not find this to be an issue. The All Music Guide covers many, many more releases, including many that are out of print, which is a big advantage over the Penguin. Of course,now, with streaming services, it’s easy to just listen and decide what one likes. But I began exploring Jazz before the advent of streaming, so these Guides were my main resource.