Very well put. I would add that it could take decades to "iron out" the issues with iPSCs. It could also never actually happen. For example, the iPSC generation process induces oncogenic properties in the cells ( https://www.ncbi.nlm.nih.gov/pubmed/22998387 ). It could be that in the next few decades, iPSCs just turn out to be a lot less safe than embryonic stem cells. Considering the hundreds of millions of dollars it could take to move stem cell therapies like this through the validation and regulatory approval process, it would be foolish to handicap the process by using "unproven" iPSCs in favor of "gold standard" embryonic stem cells.