It doesn't sound like a big difference but 40fps is actually about halfway between 30fps and 60fps in response times. Because 30fps is 1 frame every 33ms, 60fps

It doesn't sound like a big difference but 40fps is actually about halfway between 30fps and 60fps in response times. Because 30fps is 1 frame every 33ms, 60fps is 16ms. 40 fps gives you 25ms.