What's the deal with those pen displays versus iPad for drawing?

Pen displays are basically external drawing tablets with built-in screens, so you're drawing directly on what you see, which feels more natural for a lot of artists. iPads are more versatile all-around devices but the parallax (slight offset between your stylus and the cursor) can be annoying for precision work, though the newer ones have gotten way better. If you're doing serious illustration work and already have a desktop setup, a pen display like a Wacom makes sense, but if you want portability and don't mind the learning curve, an iPad is hard to beat for the price and software ecosystem. Honestly it comes down to your workflow and budget - some people swear by pen displays for the accuracy, others prefer the iPad's flexibility.