None of them is "best". You need to keep up on all three. Now, if you're applying for a specific card and you know which CRA they use then one might be worth considering over the others but it's also possible that the card issuer could pull more than one.
half of the way wrote:Was it wrong that I was told the best reporting agencies in order are (1) Equifax (2) Experian (3) Transunion.
Sounds like a dubious source. As always, consider the source.
Also keep in mind that "best" doesn't really mean anything without qualification no matter what the topic. Best in what way(s)?