You don't have to choose.
After lesson 6 you might be thinking: "OK, Shopify is cheaper at my volume. Time to shut down Etsy and move over."
Not yet.
The vendors who do this well almost never pick one platform over the other. They run both, for different reasons, and let each do what it's best at.
The model:
Etsy is your discovery channel. Shopify is your brand home.