My experience comparing GPT-5.5 and Fable:

GPT-5.5 is better for:

- Strategic thinking

- Long-form writing, including essays and white papers

- Image creation

- Code generation

Fable is better for:

- Using tools

- Testing code

- Working in live environments

- Making changes to existing software

- Creating polished PowerPoint and Word documents

Fable’s tool access is its biggest advantage. It's hard to describe but Fable ability to access sandbox environments with way more tooling can quickly become a superpower in now workflows.