Why does Google Drive not sync files as efficiently as Dropbox?
There are some good articles that present a comparison of DB vs GD.
One of the many articles can be found on MakeUseOff:
Another good article is from LifeHacker.com:
One thing to keep in mind is as OronJ mentioned, the local network could play a big part.
This would be difficult to answer without being intimately familiar with the code of both systems. That said, Dropbox uses a number of clever optimisations to speed things up:
One issue with GD is duplicate files.