I had this dilemma, then realised for the price of one ultrawide I could have 3 27", so now have 2 side by side and one on top of the right hand one (this is used for email and instant messaging). I use a little bit of software called Divvy, which allows you to set up zones on your screen and then use shortcuts to send windows to those zones, means I always have perfectly tessellating windows which makes me happy.
I had this dilemma, then realised for the price of one ultrawide I could have 3 27", so now have 2 side by side and one on top of the right hand one (this is used for email and instant messaging). I use a little bit of software called Divvy, which allows you to set up zones on your screen and then use shortcuts to send windows to those zones, means I always have perfectly tessellating windows which makes me happy.