DS did Singapore up through 6B, and then started AoPS Pre-Algebra but felt just "meh" about the first couple of chapters. He then did Elements of Mathematics 1-7 and LOVED them. This fall, I put him back into a virtual charter that has AoPS online courses as a vendor but not EoM. DH is balking at paying for the next set of EoM courses ($155) when the charter will pay for AoPS.
In giving DS the post-tests for the pre-algebra 1 and 2 courses, he knew everything aside from the chapters on square roots and geometry. So he's now working through those. Again he's feeling "meh" about AoPS.
I have heard people say that their student enjoyed the AoPS Intro to Algebra book much more than the pre-algebra one. But I don't know if my DS would feel the same.
I feel like if EoM is a solid program (which it certainly appears to be) and DS loves it, why change? But DH feels that if both are solid but one is free to us and the other costs money, why pay?