The USD documentation states that defining Prims and reparenting prims are some of the sloweest operations that USD does.
That said, USD's Sdf API is fast at authoring PrimSpecs so when I ran across a suggestion the in USD forums to split an export into two passes (one for the PrimSpecs and one for the Properties/Attributes), I had to test it out.
On my machine, the SDF version is over 100x faster than authoring the same Prims in a USD stage!
auto prim_spec = pxr::SdfCreatePrimInLayer(layer, path);
prim_spec->SetSpecifier(pxr::SdfSpecifierDef);prim_spec = Sdf.CreatePrimInLayer(layer, path)
prim_spec.specifier = Sdf.SpecifierDefhttps://groups.google.com/d/msg/usd-interest/Bh6_sxij-f8/3UYUui3cAQAJ
https://groups.google.com/d/msg/usd-interest/Bh6_sxij-f8/rnGtLK3tAQAJ