Captions excels at taking video you've already shot and making it scroll-stopping with AI-powered captions, editing, and effects. It's the tool for teams drowning in raw footage who need to ship polished content fast. Synthesia, meanwhile, generates video from scratch using AI avatars—no cameras required. It's impressive technology that solves the "we need videos but have no one to film" problem. The fundamental difference isn't quality (both deliver solid AI output) but philosophy. Captions enhances reality; Synthesia creates synthetic presenters. This means Captions feels more authentic for customer-facing content, while Synthesia shines in scenarios where a human presenter would be repetitive or impractical—think internal training modules or multilingual product updates. Choose Captions if you're creating social content, testimonials, or anything where human authenticity matters and you have source footage to work with. Pick Synthesia if you're building a training library, need videos at scale without on-camera talent, or want perfect consistency across dozens of similar videos. Most marketing teams will get more mileage from Captions; L&D departments and global communications teams will appreciate Synthesia's unique capabilities.