Do you want a channel tool or a suite?

Postscript is a channel tool. That is not a criticism. If you want Shopify SMS, a focused product can be exactly right.

Klaviyo is a suite. Its strength is that email, SMS, segmentation, product data, and reporting sit together. That matters when you want coordinated journeys instead of separate channel tools.

Where Postscript wins

Postscript wins when you are happy with your email platform and only want better SMS. It is also a cleaner choice when your team thinks of SMS as its own program with its own strategy, budget, and reporting.

Where Klaviyo wins

Klaviyo wins when email is still the center of retention. Most ecommerce teams send more email than SMS, and Klaviyo is built around that reality. SMS becomes another channel in the same journey, not a separate system.

Where Sequenzy fits

Sequenzy fits when SMS is not needed at all. If the work is welcome sequences, abandoned cart email, post-purchase education, newsletters, transactional email, and subscription lifecycle campaigns, a simpler email platform is easier to run.