Google Drive recently added selective sync to its desktop clients. I am focusing more on GDrive than on Dropbox lately, but one feature missing was the ability to selectively sync the data. It was sync all or nothing. It is a problem if I have lots of data and I want to sync data with my smartphone, whose storage space is at a premium.
Starting version 1.29, we can now choose to selectively sync. To get to this option, open the client and go Preferences.
The default setting is to sync everything, so you will need to enable the selective sync option if you wish to use it. From there, you can check the folders you want synchronized.
For more information, read the Help article here.