It depends on what your business needs are. If you're selling e-Commerce products and selling on Shopify, Klaviyo will provide you with the deepest level of integration out of any email platforms out there. If you're doing SaaS or something else, then you may want to consider other alternatives such as Active Campaigns or one of the above suggested ones. I'm a registered Klaviyo Partner and specialise in Email Marketing Automation for 7-figure eCommerce stores so if that fits your need, please reach out :)