I will try to make an objective answer, not one based on my opinion.
1. Know your drawing habits
If you want a tablet you probably have been drawing for some time. So let's discover some of your drawing habits.
A) Some people draw with only the fingers, probably you only need to make some quick diagrams where precision is not very important. Using only the fingers make less precise strokes because there are many muscles and bones involved, but saves you space and is faster to produce.
B) Some other people could use the wrists as the center of the strokes.
C) And you also could use the full arm, not only the elbow as the center of the strokes.
2. Know the dimension of the tablet
A tablet has two important dimensions, one exterior, the full device, and one interior, the drawing area. See the specs of the tablets you are interested in.
3. Make some tests
Cut a piece of thick paper the size of the exterior, and draw a rectangle of the size of that interior. Sometimes the drawing area is not perfectly centered, but that is not that important.
Take this prop tablet and draw or imagine drawing some of the work you have previously done.
Make the same with the other dimensions of the other tablets.
Remember that when using the computer you can zoom in or out, pan, and probably rotate, so what you want to measure are your single strokes of a series of them to make one shape, not to make an entire work.
4. Measure your drawings
Take now a rectangle of paper of the dimensions of the drawing area of the tablet and put them over some of your drawings and imagine if you are comfortable using that space for the same drawing.
You could also take a photo of this drawing area, a close-up, and enlarge it on the computer. Imagine this area covers the full screen.
5. Use the prop next to the computer
See if it fits in your working area, you probably need to keep space for the mouse, draw on that same working space, make some strokes. Vertical lines, horizontal ones, curves.
Do the same with the other props and compare.
Now you have clear information on what dimensions you need to comfortably use it.
You can always reduce the "sensitive" area on the tablet inside the software, but you can never go beyond the physical drawing area.
The more practice you have drawing the more fluidity you will have, sometimes doing small drawings are auto imposed expressive restrictions. It is more likely that you will use more arms in the future.
Some work is not drawing, some of the work is "painting", including photo retouching. That needs less precision than drawing, so sometimes a smaller tablet or area is a good thing.
If the dimensions of the main monitor are too big, you will probably feel weird making some small movements on the hand and see them amplified on a big screen.