The honest answer: it depends on what you're building.
Substack is a magazine masquerading as software. The recommendation engine grows new writers faster than any other platform on earth, and the Notes feed gives you a built-in audience to talk to. The trade-off is you don't fully own the relationship and you pay 10% on every paid sub forever.
Beehiiv is software that respects you're building a business. Boosts let you buy growth at a known CAC. The ad network turns idle list size into revenue. Custom domain on cheap tiers, real segmentation, an editor that's catching up fast.
If you're finding your voice: Substack. If you've found it and you want to build a media company: Beehiiv.
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