Software-as-a-Service (SaaS) has gained tremendous popularity with merchants in recent times. Merchants are looking for a stable website that won't "go down", all with minimal maintenance costs. SaaS generally delivers on these promises.
The bigger question ends up being: which SaaS platform? Shopify is often considered, but it has several significant detractors. BigCommerce is regularly our choice as it's highly flexible yet retains the security and maintainability of a SaaS platform. The Gartner Magic Quandrant names BigCommerce as a Challenger. Thus, BigCommerce is the platform we most regularly reach for.