I do have a stable connection, indeed I have been able to upload a 40GB file to Onedrive in 25 minutes. Trying through the Dropbox web interface in IE and the same file just errors out after half an hour or so with no usable error message. Tried with Chrome as well and it just sits there for a while showing no progress and then errors. Finally tried to install the desktop app but the machine is a 2008 server and the app just gives a blank sign in page during setup.
Uploading via a web browser is terrible. I have a 1gig upload/download connection. You MUST use the actual app if you want to upload a decent amount of files. The web browser method just simply does not work and will result in a lot of files not being uploaded. A few small files are OK, but don't trust it when uploading an entire folder or large files.