Of course you want cintiq as big as possible but not tablet. With A4 you get to a point where you have to move a lot around the table with hand in front of you while you are looking straight at your screen its just akward. You dont have space for keyboard etc.

I can corroborate this. A full size tablet is not always ideal. Display tablets like Cintiqs benefit from larger size because you are drawing 1:1 on a screen. The size allows for comfortable viewing as well as full arm movements on a surface that resembles a drafting table. However, traditional graphics tablets require you to draw on a separate surface while looking up at a monitor. The screen is mapped to the tablet surface, so to move the 10 inches on a 27" monitor to reach a button, you might instead only move your pen tip 1 or 2 inches. In this case, it's often easier to draw using small movements, and zoom in and out as required to work on structure or detail.

Using a large tablet is like using a mouse with the sensitivity turned down. It quickly becomes frustrating having to move your arm around so much to manage the interface, especially when you don't have a direct connection between what you're looking at and touching.

The difference is why someone might use a steno pad or moleskin journal rather than a full-size legal pad.

An illustrator friend bought an A3 Wacom years ago. It was so big that if you put legs on it it’d be a reasonable sized desk by itself.

He ended up changing the mapping to only use a small portion near the front as he could barely reach the back.

I'm doing this for my A4-sized tablet too. At times. I still have the option (and I'm using it) for the full tablet area. I don't have this for the postcard-sized scribblers.