Both complementary and competitive. USD is a much more complex beast with powerful composition workflows that allows for meeting the needs of large productions

Both complementary and competitive. USD is a much more complex beast with powerful composition workflows that allows for meeting the needs of large productions. Gltf is more of a distribution format at the end of a production like this. So in this regard they're complementary. USD can also be extended to read other formats like alembic and obj and present it as if they were USD data at runtime. A gltf plugin could be made for USD to allow gltf to act as a leaf node. There is also a packaged variant of the USD formats called usdz which is what Apple uses for their AR ecosystem. This can be seen as competitive to gltf since they are both now distribution formats and not production formats first.