I didn't realize! Figuring out the best "Henry" food is a huge challenge. A real surprise is that there is so little control over the ingredient sources. The component percentages might be fixed, but the sources are not. One lot might be made from human grade materials - and the next imported from who knows where made out of questionable stuff. They are not required to tell the consumer.
While cruising the Internet, another large frustration has been that it is not always obvious who funds the sites. The same food raved about on one site is often panned on another and I don't know enough to tell why - other than that they are, perhaps, funded by a source that counts the various ingredients in ways that pump their product score.
I did find the following source. It seems to give lots of information in an unbiased way. The explanations are clear and there is a lot of information connected to the gradings.
Check it out if you have time and tell me what you think.