Yes having a large monitor can increase your productivity by allowing you to have at least 2 browsers or other documents open and have them large enough to work between both documents or browsers at the same time.
It's also much easier than switching between dual computer monitors when working on the internet or your other documents.
I used to use 2 computer monitors but then decided to get one large monitor and it makes things easier to see and helps me be more productive and it's a lot easier than switching between computer monitors.