Even if you trust what people say on their sites about keeping it private, it still is putting your files into the public domain in some form or another. The site can be compromised, or can be ordered to disclose your information by the local authorities.

Even if that were the case that this did not occur, on a corporate network it's also very likely our out and inbound traffic is also been analyzed. 

Using qrcp keeps it local, and that means transfer is as fast as it can be, but it also means it never goes out.