Upgrading to 144hz. Will I notice a difference in rfactor 2 ?

As other have explained, it's not a matter of time, but space, as we are talking about moving object. Whatever the brain delay we can have, having more FPS is like having the same image at higher resolution: smaller the pixels get, more precision you have in deciding where to place a specific pixel. The same apply in time. Yes human input can happen between frames, but usually we tend to wait for a specific condition to be true, for example, having the distance plate of a turn in a specific position on the screen. More FPS mean the chance to pick that time much more accurately.

 

Sorry but this is not right! Latency is the most important factor when you simulate racing. Thats one of the major reasons why rF2 is as successfull and been used in real f1 out there. everything adds latency, cables, computing, you, devices, etc. Human reaction time can be a lot lower than 200ms. Human reaction time comes ontop of that. Sound also has some latency (a bit less in win10), as soon as you recognize a change your reaction time comes on top of this. And some ms too mich decide if you re able to catch the car or not. driving it on the limit means you are always running in that tricky area. 60hz is a real show stopper. I agree the step from 120 to 144hz is a small one, but i even felt that difference.

Even with 100% accurate physics, the latency of the simulation and all the devices needed comes ontop of the reality.

There are a lot of reasons beside latency to produce panels with 200+hz.
A good ressource:
http://www.blurbusters.com/