MacBook Air 13 or 15 inch?

I am considering to buy a MacBook Air M3. I currently have a M1 base model MacBook Pro, and an iMac M1. I want to have a future proof laptop to use everywhere, at home and underway, as I don’t plan to replace the iMac when that one becomes obsolete.

Now the question. Should I go for a 13, or a 15 inch? With the lid closed you can use it with 2 external displays in my home setup, but maybe is with 1 and a 15 inch screen big enough? I mostly use it for reading lots of documents and writing lots of stuff both at home and on the go.