GPT-5.6 Luna and Claude Fable 5 sit on opposite sides of Vizify’s access-tier line: Luna is Basic, Fable 5 is Paid. That single fact does most of the practical work when deciding between them, since both currently accept the same text-and-image input and produce text-only output in Vizify’s app profile.
If your account doesn’t have Paid-model entitlement, Luna is the way to reach text-plus-image chat today without upgrading. Once Paid access is available, Claude Fable 5 becomes an option from the same model picker, alongside GPT-5.6’s own Paid variants (Terra and Sol) if you’d rather stay in the GPT family at that tier.
This page intentionally stops short of claiming one family reasons or writes better than the other — Vizify’s catalog does not expose that kind of comparative data, and this product runs one selected model per request rather than a side-by-side test. Use the tier and modality facts here to pick a starting point, then switch models for a later request if the task changes.