AI today has three layers: models (the core intelligence like GPT-5.2/5.3, Claude Opus 4.6, Gemini 3 Pro), apps (the interfaces you use to access them), and harnesses (the tool systems that let them act autonomously) and choosing the right AI now depends on how these layers combine for your specific task.
https://www.oneusefulthing.org/p/a-guide-to-which-ai-to-use-in-the