HD to SD export process
 

Everything I have read, says to export from FCP as a apple pro res 422 file, then drag this into compressor and export as a best quality SD DVD setting. What is the reason for exporting as Pro Res first, and not just exporting with compressor as best quality DVD straight out of FCP?
I have read a lot of articles on it, and haven't heard of one person doing it through compressor first, and I wondered why.

the exported prores clip can server for multiple outputs, and as a master archieve of the entire project. also FCP->compressor export is very slow, about 2X slower then the direct export. this again becomes a problem when making lots of different exports for web, DVD, ect.