Hi @Kamy, nice to see you here in the community.

Now, as a disclaimer, I’m a Partner of Klaviyo and I think you probably should expect some bias towards Klaviyo here in the community, but I do have some limited experience with Sendinblue (migrating to Klaviyo ironically).  

On surface, Sendinblue does look compelling and it has a lot of feature sets that are unique to their platform.  However, since you have a custom ecommerce platform, it really is down to the API capabilities, developer support, and long term roadmap that I think you should take into consideration. You can see Klaviyo’s API developer portal here: https://developers.klaviyo.com/en/

Under the hood, I see Klaviyo fundamentally as a “data platform” that takes (ingests) data from multiple sources either from pre-built integrations or via custom API.  And then, Klaviyo lets you utilize that data to build powerful segmentations and automations with Email, SMS, and Push (or other external systems via webhooks).  On the surface, many ESPs appear to do the same thing, but when you dig deeper, the differentiation starts to be more obvious when you have more complex or sophisticated use cases especially with platforms that are not ecommerce oriented (it’s either general purpose, or tries to be applicable to every industry or vertical). Klaviyo started in ecommerce, and for all that I can tell, will stay focused in this vertical because I imagine 99% of Klaviyo user are merchants.

For example, Sendinblue doesn’t have the notion of a Product or Catalog Feed - because they serve not only ecommerce companies (where typically a physical product is represented) but also other industries like SaaS, Media, Finance, etc.  You can pass it custom events with product information (price, item name, sku, qty, etc) - but it’s not fundamentally a “first order object” in their API.  So referencing products in your templates is a manual effort on your part or you have to spend the time to build your own tools or scaffolding to make the day to day management of email campaigns (or automations) with products in them easy to execute. 

This isn’t necessarily a criticism of Sendinblue, but because they need to serve multiple industries and customer types, building a “Product Selection Tool” in their Template Editor wouldn’t necessarily be their top priority since it won’t be leverage by folks who use their platform to send Insurance Quotes, Hospitality Reservation System, or a SaaS tool, etc.  This is just one example that I could find, but philosophically you can see how there may be other “missing features” in other areas when you get down to the details. 

Finally, I find the Klaviyo support teams to be helpful, the amount of documentation and resources they produce invaluable, and the community at large to be super resourceful and helpful (like here!) - not to mention Klaviyo’s robust and widespread ecosystem of apps, agencies, and integration partners a real major long term future-proofing benefit that’s not immediately obvious when you just look at the specs.  Those are my opinions of course! 

I do hope you choose Klaviyo, I think it’ll work out for you long term. If you want to learn more, I highly recommend looking at these guides for custom ecommerce platforms:

• Integrate a platform without a pre-built Klaviyo integration

Best of luck!

Thank you! Yes, I knew that the perspective provided here would be biased, but that’s ok. I very much appreciate the intel.