Klaviyo is a powerful email marketing and SMS tool that excels in e-commerce personalization and customer segmentation. It offers deep integration with popular e-commerce platforms, making it ideal for online retailers looking to boost sales through targeted campaigns. Customer.io, on the other hand, shines in creating complex, multi-channel marketing workflows and is particularly effective for businesses that need to coordinate messaging across various channels. Both platforms have strong automation capabilities, but Customer.io offers more flexibility for businesses outside the e-commerce sector.