Magento vs Shopify Plus vs Shoper vs Atomstore for the Polish market, which one?

Four real options for Polish merchants, very different ceilings:

• Shoper, Polish-founded SaaS (Kraków), dominant in the PLN 100k, PLN 5M segment, BLIK + Przelewy24 + PayU pre-integrated, Allegro feed native. Cheap (~PLN 100-500 /mo). But you hit ceiling on custom B2B, multi-store, and ERP integrations.
• Atomstore, another Polish SaaS, strong on B2B + omnichannel, but smaller ecosystem and locked to vendor.
• Shopify Plus, great DTC UX, BLIK supported via Stripe Poland or third-party apps, but Allegro feed needs paid apps (BaseLinker / Channable), KSeF e-invoice isn’t native, and B2B is limited.
• Magento 2 / Adobe Commerce, ceiling unlimited. Full BLIK + Przelewy24 + PayU + Tpay stack, KSeF XML pipeline buildable, NIP + REGON validation via GUS API, Allegro multi-account feeds, multi-store PL + CZ + SK + HU on one backend. Higher TCO but pays back at PLN 5M+ revenue.

Rule of thumb: under PLN 5M revenue, Shoper or Shopify; over PLN 5M (especially B2B or Allegro-heavy), Magento.