Upload & Sell: Off
It will vary a bit with how you use Lr. e.g. I often whiz through lots of photos in the Develop module and/or in the Library module and so the file access/retrieval/storage time is relatively significant. Others might spend far more time per photo and in that case their editing/viewing time far outweighs the file access/retrieval/storage time.
My preference is as follows:
OS and all software on the SSD to make the whole computer feel snappy.
Lr catalog on the SSD to speed up Lr.
Lr previews on the SSD to speed up the Catalog module and to a lesser extent the Develop module.
ACR cache on the SSD to speed up the Develop module.
For initial file transfers from camera cards to the computer I put my files into a dedicated Lr auto-import folder on the SSD and work on them there because that is faster. Once the bulk of the work such as rating, labelling, preliminary editing, keywording, etc. has been done I use Lr to transfer them to a permanent home onto a slower HDD. They'll generally get less editing done on them there and the preview cache on the SSD may be all that Lr needs to let me see them quickly in future.