If you look at art history, you will discover the artists constantly experimented with new technologies, chemistries, methods, etc. I think that iPad + Apple Pencil is one of the latest additions to the artist's collection of tools. Personally I find that taking a photo and then using it as a layer to draw on top of is very helpful for some exercises, especially when beginning to learn cartooning / caricature drawing.

Personally I use a Lenovo (Android) tablet with AutoDesk SketchBook and an Adonit Dash 3 stylus. A good, cheaper alternative to Apple products. The biggest drawback being that there is no palm rejection with this approach and that can be an annoyance at times.