4. On-Screen or Flat Models. Although choosing the one over the other might be of two worlds apart when it comes to user experience, you have to consider your design options. If you tend to be mobile, you might opt for an on-screen pen tablet such as the iPad. If your stationary all the time, you might need only the flat ones that needs monitor. Or better yet, both.
5. Resolution. Resolution matters for designers and illustrators of large-scale projects. You need to consider LPI (Lines Per Inch) for you pen tab when choosing your unit. The higher the resolution, such as 4K monitor compatibility, the brighter and crispier the images produced by your artwork.
6. Built-in Scrollers. Monitors and graphic pen tablets are two worlds apart. Scrolling using your tablet versus a mouse might be of different experience, so you might want to consider this functionality before buying one.
7. Wired or Wireless. These two forms has advantages and disadvantages of themselves. Wired being stable because it is being hotwired to your monitor, so no fear of signal lag and interference. Wireless on the other hand, gives you the luxury of mobility, but lag and signal interference will sometimes gets into the nerve of your projects. No worries, this is more likely not to happen than it would.