Ecosystem vs native
Both are hosted SaaS commerce platforms, which makes this a fair fight unlike WordPress-vs-Shopify. The difference is philosophy: Shopify ships a focused core and routes complexity through its enormous app ecosystem (paid, mostly); BigCommerce ships more native features per plan, fewer apps to buy, fewer moving parts, thinner ecosystem.
Shopify wins when
You want the gravitational center of ecommerce: every payment, fulfillment and marketing tool integrates first with Shopify, hiring is easy (specialists everywhere), the theme and app market is unmatched, and checkout optimization is a science. The costs: app subscriptions stack quietly, transaction fees apply off Shopify Payments, and advanced B2B needs price accordingly.
BigCommerce wins when
Native breadth beats app stacks: strong product filtering, price lists, and B2B features included on mid tiers; no platform transaction fee on any plan; headless APIs are first-class. The costs: smaller specialist pool (fewer BigCommerce-native developers and agencies), smaller app market, and a community that answers slower.
The buyer math
Small-to-mid store, mainstream needs → Shopify's ecosystem and hiring depth usually win despite app costs. Feature-heavy catalog with B2B pricing on a budget → BigCommerce's native stack can undercut Shopify-plus-apps meaningfully. Either way: hosted platform equals platform rules, monthly forever, and exit-is-rebuild (the standing caveat).
Undecided in one sentence?
Describe the catalog size, B2B needs, and monthly order volume, the answer falls out fast. Send exactly that, or start from the Shopify service page for the build-side view.