First off, the human eye is real time, it doesn't operated on "frame rates" it is all one continuous stream. It is the brain that converts the individual pictures into motion. Each brain is a little different but in general if the frame rate drops below 17 or 18 FPS, the motion stops and it looks like you are in a night club that is using strobe lights.
At 17 FPS you wind up with "true motion", sorta kinda. A picture of a person walking down a city street looks ok, but when a car passes you get a blur. (There is actually some blurring on the walking person but it is almost imperceptible). At 24 FPS (cinematic speed) the car is still blurred but it is recognizable. At 30 FPS the car is still blurred but you can read the car's license plate. At 60 FPS the blurring will be almost imperceptible. Take that same car at 60 FPS and put it on an expressway, and you have effectively reduced the detail down to around where is was at 24 or 30 FPS because it is moving faster now.
If you are just standing there watching the car with your hands in your pocket, 30 FPS or even 24 FPS is good enough, but if you have to drive it at 30 FPS, you are going to be all over the road and eventually you are going to run into something. The reason is that when you try to turn the steering wheel, the car will not immediately turn, it can take anywhere from a half second to a full second for the car to react and at 70 MPH, that is deadly. (For those of you that live in the Old World, I have gone through the trouble of converting 70 Miles per Hour for you into Old World measurements, just for you. Yes, I really am that nice of a guy. 70 MPH equals 188160 furlongs per fortnight.)
Basically, higher FPS gives you better control in a fast paced environment.
Having said that, most of the time spent in the Fallout Universe is spent in fairly slow paced tasks. Exploring, trading, talking do not require fast response times. In situations like we find ourselves most of the time, 30 FPS is more than enough and detail (higher resolution) is important.
This whole discussion revolves around personal preference. Some people want as detailed and vibrant a world as possible. Others are willing to sacrifice a little of that detail for better response times in a fight. There have been attempts to satisfy both crowds by using dynamic frame rates and resolutions, but that has very seldom worked in a way to satisfy everyone. Some people find the experience quite jarring. And there is a problem of a lag effect at the beginning of a fight.