You get different answers depending on who you ask, but let's consider the factors in play: temperature and yeast quantity.
The temperature of beer in a carboy will stay more stable because there is more liquid than in a bottle. This probably makes little difference on beer time scales, but in winemaking this is a big factor.
There is more yeast in a carboy than in the bottles, both in the aggregate and per unit beer. Yeast is responsible for much of the aging process, so more of these processes will take during 3 weeks of aging in a carboy than in a bottle. This difference is probably not very large either.
On the flip side, yeast tend to make a little bit of funkiness when consuming the priming sugar, so additional time in the bottle is needed for re-uptake of the funky compounds. So, if you were to age it in a carboy, you'd still have to age it at least a small amount in the bottle anyway.