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.
I just installed Box to take advantage of the free 50gb. The one critical thing I think Box is missing over Dropbox is being able to take advantage of sym links. Until then, Box is a boy among men.
For us this means one thing: There is a well-supported and maintained Linux client that just works.
I've no doubt we'll be giving Dropbox for Business a try, but it's pretty much because of the ubiquity rather than anything else.