Caution!
I set up a simple sync of a folder between Dropbox and OneDrive to test the service, on a free plan limited to 5GB a month. On the plus side, I like the interface and the set-up was very easy. HOWEVER, even though the folder was only 1.7GB, they kept insisting that I had used up the full 5GB and cut off any further syncing until the next month. This left me with the feeling that if I had had a paid plan with capped monthly transfers, they would have pulled a similar bad faith stunt and short-changed me. Pay them at your own risk! UPDATE - to reply to the useless response from Multcloud shown below: of course I tried Technical Support, that's who kept insisting I had used 5GB syncing a 1.7GB folder! Wasted enough time with these guys, trying the better-known alternatives instead (not going to name them, don't want to seem like I'm shilling for them)