It seems that both terms are used to refer to beadwork but beads art seems really weird to me (think Dogs Food).
To be clear, I am not only referring to the rules of usage. I would like to know what is the most common usage - this is important for us as we need to use the preferred copy in our prints. If "bead art" is technically correct, but most people don't resonate with the term, then we would still go with "beads art". Most of the people in my company insist that it's "beads art". I think it's "bead".