Shopify Messaging

If your store is already on Shopify, I would say their app is the way to go. I went through trail and error comparing Shopify Email with Mail Chimp and Constant Contact... I found that Shopify had better-looking layouts and style options that matched my brand. The fact that my products can link directly to the marketing email is deciding factor alone. My only reservation(s) are I wish there were more options to personalize the design of the emails even more (borders, different shapes/sizes for buttons, etc) but the I see how the standardization makes sure your design will render well on various screens. Also, they do not make it easy to add email subscribers-- but not a deal breaker for me.