Klaviyo is built around the product-purchase event stream. It knows what your customers bought, when, how often, and uses that to drive segmentation and lifecycle automations. For a Shopify store doing real revenue, the lift over a generic platform is dramatic — the abandoned-cart and post-purchase flows alone usually pay for the upgrade.
ActiveCampaign is the better answer the moment your audience isn't a product-purchasing customer base. SaaS teams, agencies, info-product creators, course businesses — anyone whose marketing motion is content + nurture + sales conversation rather than transactional commerce — gets more out of AC's automation builder and embedded CRM.
Cost-wise: Klaviyo prices on contacts + monthly send volume, ActiveCampaign on contacts × tier. At ~10K contacts both land in the same ballpark. At 100K contacts the math diverges based on send volume — model it before committing.