@PeterFalkingham
I do a lot of stuff on an iPad now, because the pen experience is so much better (half the latency of a Wacom). The best painting app is Procreate.
On my computer I use Photoshop, although Affinity Photo and Pixelmator Pro both work for me. Painting is not really demanding in terms of features, they basically just have to avoided screwing it up.
@mike Much bigger dynamic range, and more data to work with than a JPEG - so it's easier to brighten the dark areas or darken the bright areas of an image later, for instance. Basically, more info stored in the image than in a JPG or TIFF.
More complexly, it's the raw data from the sensor of the camera, before any processing or denoising etc is applied.
I don't often use them, but in this case I've got some sunset/snowy pictures I'd like to play with contrast and exposure on.