I have 3 answers: Short, Long, and Longer.
SHORT answer: If this is being edited in a DV-timeline then what you have in the Final Cut timeline is exactly the same as what will end up on that DV tape (with a firewire connection).
So the short answer is, no, it doesn’t matter if you come right from Final Cut or dub it to DV tape first.
The LONG answer is “maybe.” For example, if your Final Cut system is hooked up to a BetacamSP deck with a Y/C cable then it would not be as good as if you had a DVCAM deck hooked up to a BetaSP deck with Component cables. But if your DV deck just has composite out, suddenly the Final Cut option is better.
So really, it depends on the connections available to you.
The even LONGER answer is this: The absolute best quality would be to copy your project into an uncompressed SD timeline. Convert your source footage to uncompressed video and re-link the files to the new, converted video. The video won’t look any better but any effect, title, or color correction you do would benefit from existing in a less-compressed sequence. In that case you’d not only have to have a storage system capable of running uncompressed SD, but also a good connection from a computer to the Beta deck. In that case you could NOT go back to DV tape without losing the extra quality you gained.