One of my favourite things about these two episodes is Moffat's snappy and clever dialogue. There are so many quotable lines!
If I had to pick a favourite, though, I think I would go with this exchange between the Doctor and Rose in The Doctor Dances:
Rose: Okay, so he’s [Jack] vanished into thin air. Why’s it always the great looking ones that do that?
Doctor: I’m making an effort not to be insulted.
Rose: I mean… men.
Doctor: Okay, thanks. That really helps.
What's YOUR favourite quote??