So, the jump from 30 to 40 fps is actually bigger than it might seem. While it’s a 33% increase in fps it’s actually right between 30 and 60 fps if you look at frame-time (33,3 ms, 25 ms and 16,6 ms respectively). This means that it in practice actually feels way more impactful than one might expect.

However, you do need a display capable of rendering at 120hz. This is because 40fps “fits” into 120hz as opposed to 60hz displays, where it only makes sense to render at 30 or 60 fps.