Please note that the image is not presented as a "proof" because I'm not trying to prove anything, like dropbox or onedrive are "bad" and I'm not accusing any of these provider of "interruptions". They are free services (well, not onedrive for business) and we have to be grateful for them. Actually I changed my mind, I do accuse someone - Microsoft's OneDrive for Business upload behavior is pathetic. This. I said it.
This is why I didn't even save the image segment of box.com's upload. You will have to believe my word
This was just my experience. My post is meant for other to realized that expectations and fact are sometimes quite different. So it's better to test before preparing to move your books collection to a cloud drive. Form me it's clear that on dropbox I will have more than twice longer upload times than on google and box.com.