we tried box and dropbox and went with dropbox as it supports LAN-Sync (tremendously helpful when you are shoving around Photoshop files) which box didn't at the time and the Linux client.
On the same topic, we thought about btsync as well. But ubiquity won out, there's a lot of convenience in being in a meeting and being able to check your phone and pulling up the latest copy of a document.
box lets you pull up a file on your phone... we find the versioning and collaboration features of box to be far supperior to dropbox... lan sync is nice though, I didn't actually know dropbox had that.
In addition to these, the inability of box to handle mac bundle type files was a show stopper.