I use my ipad pro / pencil as a sketchbook. As far as a portable digital drawing platform, I felt the iPpro was the best offering when I went and tested a bunch of options last year. It’s still no wacom, but pen response was far more reliable and accurate than on the android and Surface devices I tried. Using a textured screen-protector really helps a whole lot with simulating the feel of pencil on paper, as opposed to the zero-resistance fell of the plastic stylus-on-glass.
The current adobe mobile apps are not full ports of the desktop programs, although photoshop is supposedly coming soon, and illustrator will follow eventually. The Draw app is still very useful for getting ideas down on ‘paper’ in vector format, and with a CC subscription everything is saved to the cloud and immediately available from the desktop app for further editing/manipulation.
Most of the “menu operations” (for lack of a better term) that I use in AI still require the desktop version. This hand, for example, was drawn in Sketch, but if I wanted to knock out some layers for engraving, merge the individual strokes, and make a cut outline, I would need to send it over to the desktop.
I don’t do much raster work on the ipad, but I did buy Procreate, which has a lot of great drawing features built-in, and is able to be expanded with add-on brushes and such.
i also have Vectornator, and autodesk’s Sketchbook, neither of which I have managed to get into deep enough to have an opinion.