There is no difference between a USDZ 3D model and another USDZ 3D model in terms of format—both strictly follow the same USDZ file standard for 3D content.
USDZ is a compressed, self-contained format that packages all 3D assets (geometry, textures, animations) into one file. Any distinctions between two USDZ files come from their unique content (e.g., a chair vs. a car model), not the format itself.
To compare specific USDZ files, use tools like Apple’s Reality Converter to inspect embedded assets (textures, polygons)—this shows what makes each model unique.