I keep seeing/using free tool versions of KWfinder, Moz Keyword Explorer, Keysearch.co, keyword revealer. They all seem to have the same type of keyword difficulty. SEMRush's values are very different and always more difficult. That's confusing to me. Experienced SEO professionals seem to frown upon using anything that uses metrics that Google doesn't use. I never thought about it before, but I guess it makes sense. No one knows how googles uses those 200+ ranking factors in their algorithm so I guess these tools are just guesstimating most of the time to sell their product. I keep reading about how the only really good way to evaluate a keyword's ranking difficulty is to do it manually, but I have no idea how that is done. Is that the kind of thing that's considered a professional secret and no one in their right mind will tell me? If it's not a super trade secret, can someone give me a hand and let me know how it's done or point me in the right direction regarding what to read about it? Thanks!