We haven't used Elemental or R.E.A.L., but we have done some of the mysteries on Mystery Science and really enjoyed them. I feel you could use it as a thorough curriculum if you brought in some extra books/materials on the topics, and use their extras.
We use and enjoy apologia, but since it's topically focused, I bring in other topics by using MS. We're finishing up Astronomy, but I wanted to glance at other topics, so we recently used MS for their Plant Adventures unit. Both of my kids (7 and 9) really enjoyed that. We're moving onto Botany with Apologia next, so we'll probably use MS for topics like weather, animals, etc... The activities are simple, but provide good understanding of the topics. Also, MS is fantastic with their communication. They're quick to answer any questions you or your kid(s) may have and are very receptive to feedback.