Being able to upload and download images is great, but you're massively dependent on how strong your internet connection is - if your home has a slow connection, yet you want to back-up many gigabytes-worth of RAW files, the experience could well be frustrating. Meanwhile, one of the biggest problems with online services is that there are no promises of permanency - if the service runs out of money tomorrow, it could disappear overnight, taking your files with it. This is why we would always recommend using a combination of physical drives and cloud storage.