That wouldn't surprise me - I had seriously considered subscribing to Dropbox many times, but the price was just too high for my needs. When they forced me to make a decision (by enforcing the 3 client rule), I evaluated the costs/benefits and ended up going with OneDrive - cheaper overall and I got Office 365. I much prefer Dropbox's sync technology, but not at double the price.
What's baffling to me is that OneDrive already has the same technology as Dropbox (block-level syncing instead of the more common file-level syncing), but they have arbitrarily only turned it on for Microsoft filetype extensions (mostly Microsoft Office files). If they enabled it for all filetypes I'd switch over tomorrow.
"Differential sync brings the ability to sync only the parts of large files that have changed, not the entire file. This makes the file synchronization process faster for these files. Currently OneDrive supports differential sync for Office 2016 files. Later this year, Microsoft will bring the ability to leverage differential sync to all file types stored in OneDrive and SharePoint."
"To complement these large uploads, we announced availability of differential sync for PC and Mac, bringing the ability to sync only the parts of large files that have changed, not the entire file."
