Default Material Target Setting in USD Exporter

[wallworm]

The default material target in the USD Exporter has been USD Preview Surface for several years. With the new MaterialX Document in Maya that allows editing shaders in LookDevX, we are starting to re-evaluate the default export options for USD. While doing work on supporting the MaterialX Document in the USD Exporter, the team brought up the question about switching the default to MaterialX instead of USD Preview Surface.

We would like to hear from the community if you think this is a good or bad idea and how it might impact your workflows and pipelines. Note that USD allows multiple material targets, so we've include both USD Preview and MaterialX as an option in the poll.