Subjectively, I’ve found that compressor does a better job of encoding the video than DVDSP. The cost is a little added time to your workflow (which is very sound, btw).
If you want to try the compressor route, you should export a quicktime ‘reference’ movie from FCP, and send that to compressor. With the reference movie, your footage is not re-encoded until compressor does its work.
I’d recommend giving it a try, and deciding for yourself if the time/quality trade-off is worth it.