If you're a developer or managing a SaaS application, choose Resend. Its developer-first API and robust SDK make it perfect for creating transactional emails without the overhead of complexities found in typical marketing-focused tools. With strong deliverability and React Email for building component-based templates, it's tailored to meet the needs of tech-savvy users.
On the other hand, if your focus is on growing a media or content-driven newsletter, go with beehiiv. Its built-in referral and monetization tools are beneficial for scaling and engaging readers effectively. However, if your goal is to manage product lifecycle emails or seek simpler automation, beehiiv might not fit your needs.