To Bottle, or Wait?

I've got a sweet stout that's been 3 weeks in primary, and she's done.

I don't usually secondary, so what do you think - will it benefit significantly (flavor wise) by sitting another week, or should I bottle this weekend?

You could go ahead and bottle, but for a stout i'd recommend aging it for a couple months

Hmm. I want to give it enough time in the bottle to condition nicely for Christmas.
Maybe I'll leave it in another couple of weeks.

Well, if it's done you can certainly bottle it and let it age in the bottles for a couple of months, either way it will be aging.

I guess that's what i was trying to find out originally - if being on the yeast would be any better than being in the bottle. Do you think they have anything more to clean up?

In my experience the only real difference in letting it age bulk or in bottles is the uniformity of the product. Some bottles might be a little warmer or have a little more light on them, which will result in a less uniform product than if you were to age it longer in the carboy or bucket before bottling. I would go ahead and bottle though, no sense wasting space, specially if you've got another brew to do.