Colonies have distinct and different personalities. Perhaps the "busier" hive simply has more foraging bees while the other has more nurse bees. They are both building comb and using sugar syrup so that is good.
When I installed my two packages last year, I noticed the same thing. While one hive was doing well with plenty of bees and brood, the other hive was really kickin'.
I also noticed that the bees in this kickin' hive would crawl up the front of the hive a little bit and then launch into flight. The bees in the other hive would launch straight out of the hive opening!
Now, I know that you think that I am crazy but that goes without saying. I do keep stinging insects, you know! BUT, I moved the queen from this kickin' hive along with 5 frames of brood/honey/pollen into a new hive about a month ago. And the new foragers that have hatched climb up the front of the hive before launching into flight! Must be in their DNA!