I am very far from expert on the ins and outs of photography versus scanning when creating digital images of art. But I have noticed a couple of things. Firstly, the photographic image always shows all the colours and textures of my work, while a scanned image can easily 'hide' them, depending on the angle of view and brightness one chooses. In a scan of one work, when viewed head-on it looks over-bright and a few colours and textures are missing. It's only when I turn the screen away from me that they actually 'come into view'.
Then there is the question of the contribution of lighting. To the right is a scanned image of mine, done on black paper with coloured pencils:
And this is the same picture, photographed on an overcast day in the out-of-doors:
So which is better? In a way, the sunlight one is better because it may be easier to see the details. On the other hand, the scanned one is preferable because it shows the luminous rich pink fringe in all its intensity, not to mention the black paper in all its blackness.
Scans don't have shadows or uneven lighting or sun-glare blighting them. Yet somehow they are not the same as a photograph whose effects I find easier to assess and control. I'll do scans if the size of the work permits -- but I'll take photographs for comparison, as well.