I've tried a few of them and found the results are very similar. Megacrop 2 part is identical to Jack's a/b except that they use amino acid chelates. I get the same results with Maxibloom as I do with Jack's, but I like the flexibility of keeping the calnit separate. The only difference between these, in most cases, is price. Jack's, GH, Floraflex, and Athena are all clean products as far as heavy metals are concerned, so any of them would be a good choice. The only real difference between these is price-I suspect most of them are just rebranding Haifa salts, but they don't like to say since their brands rely on the perceived differences among them. The only dry nutrient I know for sure is using Haifa salts is Advanced Sensi Professional dry formula, which is AN's answer to the popularity of Jack's A/B. If you don't know about them-Haifa group is an Israeli fertilizer company that makes very high quality, clean salts and they do lots of rebranding. Always check the heavy metal content of nutrient salts though, because not all brands are as clean as these-some are just terrible.
https://apps1.cdfa.ca.gov/fertilizerproducts/