I use Dropbox. There are various reasons. First, Dropbox does block-level sync. If you change a large file, only changed blocks are synced. Secondly, LAN sync,

I use Dropbox. There are various reasons. First, Dropbox does block-level sync. If you change a large file, only changed blocks are synced. Secondly, LAN sync, which does peer to peer sync over a local network. Another nice feature is that you can set up file requests, where people can upload files without sharing a folder (which I often use for classes). Besides lacking these features, Google Drive had some serious deficiencies the last time I tried it. E.g., it was not possible to get a list of shared folders (besides running a Google apps script, which takes a long time to run). The Google Drive client would regularly bail out when syncing a large number of files. And they were permitted to mine user files for ads when you don’t have Google Apps for Work (and it is not clear if your files are indexed for ads if you share a folder with a non-Apps for Work user).