Magento vs the platforms Casper / Purple / Saatva run on, what is the right comparison?

Honest cut, mattress-specific:

Casper historically ran a heavily-customised Shopify Plus stack (single-SKU origin story, queen-mostly, mattress-in-a-box), then moved category-by-category to a hybrid as the catalog grew. Purple runs a custom Magento + headless front-end, full-range mattress + base + pillows + sheets demanded the SKU depth. Saatva runs custom Magento end-to-end, white-glove + LTL freight + showroom-pickup workflow only works with the level of order-attribute control Magento gives you.

The pattern: under ~$15M GMV with one-or-two SKUs the simpler stack survives. Above that, with full-range + white-glove + financing + B2B-hospitality, every brand I have seen at scale runs Magento or a custom build. Tuft & Needle (acquired by Serta Simmons) ran Magento for the same reason, the trial-window, financing, and LTL workflow needed first-class order-attribute control, not an app stack.

If you are below $5M GMV with a single mattress SKU, stay on Shopify and save the migration cost. Above $5M with white-glove + 3+ financing lenders + a full bedding catalog, Magento is the cheaper long-term answer once you count app fees + revenue lost to platform ceilings.