I never felt like I needed anything more than a 13" laptop screen. I have a 25" monitor on my desk and I almost never use it for work. I mainly leverage multiple workspaces, I think it's faster / more convenient to do Meta key + 1,2,3,4... than turn my head / eyes around between monitors. Some OSes make it sloppy though, last time I checked Mac OS has an annoying delay when switching workspaces that you can't get rid of.