Yeah, each person had importance in the Nine/Rose/Jack dynamic (which I hope will eventually also apply to the Eleven/Amy/Rory relationship as well), but there was a very clear-cut boss and that was Nine. This time, the Doctor is nominally the leader but as far as the emotional/relationship aspect goes, Amy's in charge.

It's also just really nice to have two Companions again -- correcting for differences in writing style/skill over the years, I think the show's more interesting when there are at least two Companions. Add one more character and have three times the relationships to develop!

I need a Hartnell icon, hmm.