Klaviyo shows up in every e-commerce store's email setup we checked, while Customer.io is not the tool you want for full-featured email marketing.
Only use Customer.io if you just need segmented onboarding flows or Slack updates, but stick with Klaviyo for anything more.
Klaviyo is the clear pick if you want a serious email marketing tool for e-commerce. Every e-commerce friend we talked to uses it for flows like abandoned carts and upsells, and it comes loaded with templates built from industry best practices. It's basically the default for e-commerce stores because it lets you personalize messaging and automate based on real customer behavior.
Customer.io is better if your main goal is building segmented onboarding funnels or visually managing communication flows, especially if you care about things like Slack integrations and in-app event pushes. But if you need a full-featured email marketing platform, Customer.io isn't the right call.
If you're running an e-commerce store and want proven, high-performing email flows out of the box, Klaviyo is the obvious choice. Customer.io is only strong if you're prioritizing onboarding and internal notifications over actual email marketing power.
