Wacom Intuos Pro Small or Medium

I've been using a small for years. For most things it's good enough, but Lightroom is kind of a special case.

If you're only going to use the tablet for Lightroom, spatial precision matters a lot more than pressure levels. In Lightroom, the only place the pressure levels matter is when you're painting with the Adjustment Brush, or in the mask for a Graduated or radial adjustment filter. For those uses, over 8000 pressure levels is more than you need. Because of that, it isn't even necessary to spend the money on an Intuos Pro; the full power of the Pro only gets used with the advanced interactive brushes and painting options in an application such as Photoshop.

Lightroom has a lot of tiny controls. That can make them hard to hit or drag with a stylus. It can be especially difficult on a small tablet. The problem is not resolution; these tablets have a resolution of 2540 (for the Intuos) or 5080 lines per inch (for the Intuos Pro). That's more resolution than you need for even a 4K display. The problem is that if you have to do things like drag a slider a short distance on a large monitor, that may require a very tiny hand motion on a small tablet. The medium size should make it easier to precisely control Lightroom, as long as you have the room on your desk for that size.

Aside from the additional pressure levels and resolution (which you won't need in Lightroom), the only other reason to buy the Pro is for the shortcut buttons and control dial. If you don't need those, you might consider trying the less expensive Intuos line for Lightroom.