The difference is that the light values represented in the negative are quantified by varying accumulations of physical grains of reduced silver. A metallic element on the Periodic Table. Real stuff.
Electric light values stored in the digital file are abstractions quantified by a scalar count which is substituting for the real thing. A value is not a thing. It's a description to be applied to a real thing.
Both are being used to represent something else (the image), but absent Photography, silver still exists as a physical thing in Nature, but the number '8' used to quantify a light value never did exist physically. It's an abstract concept.
Both processes are capable of creative expression limited only by the imagination of the person doing the creating.
If one's definition of Photography is based around image creation alone and nothing more, then they both would fit that definition. But if one's definition incorporates the physical nature of the original photographic process (see Maris' signature), then no, they are different. One is Photography, and the other is another form of post-Photography imaging.
It all depends on each individual's working definitions.
The physical meaning of "no space left" is that a containing volume is physically full. That the void defining that volume is now completely occupied in space and time. The water glass was empty, but now is full of water. There is no more space in the glass for additional water, and two volumes of water cannot occupy the same space at the same moment.
But in the case of a hard disk with "no space left," what does this mean? There was no physical void to begin with. An "empty" hard disk and a "full" hard disk subtend exactly the same volume in the real world. Same size, same weight.
What has changed is only the pattern of magnetised spots on the rotating platters that define the hard disk's physical reality. There are no physically "full" or "empty" conditions. A "full" disk weighs no more than an "empty" disk. There was no void to begin with, and there is no lack-of-void later.
The hard disk is a virtualized abstraction of a real world, physical container. It is designed to "hold" (there's those quotes again) nothing more than abstract data values which represent real world things. Not the real world things themselves. The abstract data itself is indirectly manifested by the patterns of those magnetic spots. The spots themselves, although physical, are also not the original real world things.
Even the physical patterns on the platters are arbitrary. If you save a digital image to a hard disk twice, the physical distribution of the spots (which platters, which tracks, which sectors) will be different. Because you have now crossed back into the physical realm of persisting those spots representing the virtual values, the constraints of space and time again apply, meaning the patterns - the physical distribution - must be different.
I've done software development and engineeing for almost twenty-five years now. And I've watched with facination as computerized virtual reality has slowly replaced physical reality in society to the point where many individuals have lost the ability to distinguish between the two.
Most people - those who would not use quotes - really do believe they are typing onto a sheet of paper. But it's not paper. It's a white rectangle generated by an electronic viewing device which is hooked to a computer which is running Microsoft Word.
Most teenagers think they have a large circle of friends. But they are not real world, physical friends. They are virtualized checkmarks next to virtualized boxes highlighted with the virtualized printed word "Friend."
A lot of people in the world can no longer distinguish between these sorts of differences. Sadly, I think, a lot of those wouldn't care even if they could.
And that, in a nutshell, is why my own preference is for the physical reality of Traditional Photography, and not its virtualized cousin. My preference is for things I can touch. True photographic negatives with a real world provenance back to the subjects they depict. First generation renderings of The Thing Itself.
If only everyone would...