If you're a newsletter operator or in a media and content business focused on growth, go with beehiiv. It offers specific features like built-in referral tools and monetization options through ads and paid subscriptions, which are advantageous for scaling your audience and revenue. However, be aware that it leans toward media-style newsletters, so if you're looking for product lifecycle email features or a simple automation tool, you'll want to consider other options.
On the other hand, if you're a creator or a solo founder who needs flexibility and strong automation capabilities, choose Kit (ConvertKit). Its tag-based subscriber management system and visual automation builder are great for crafting personalized email journeys. However, if you prioritize advanced email design or only require occasional broadcasts, this tool may not be the best fit, as its design is more functional and can become costly as your subscriber base increases.