The iPad gives you touch interaction, hand-held operation, a higher quality (albeit smaller) display, and a more resilient operating system (albeit managed).

The Neo gives you a real keyboard, a bigger screen, and unified UX/software support with your desktop computer.

But are you sure you need two devices? Why not just get a MacBook Air (with the same spec as your proposed Mac mini) along with a USB-C dock accessory to connect charging/keyboard/mouse/video with a single cable? Also don't underestimate the value of having a battery in your "desktop" computer. It's a free UPS.