What I discovered over the years is the image blurs at high line of sight rates. Higher fps seems to help, and being able to stay in vsynch and run at higher FPS is what I'm striving for.
You won't notice stuttering until less than 30fps, but there are things other than stuttering which affect visual acuity.
Then again, I was the guy who could walk into a room of CRT monitors and see the one or two which were set lower than 60hz (flicker flicker flicker). As I discovered not everyone sees that....
Anyhow, there is a reason why the flatscreen TV industry went to higher refresh (besides screaming new model! new model!) so they could "unblur" fast action scenes and sports.