Peoples perceptions are subjective but theres a ton of science that says a few key things about computer interactions we can lean on ...
- As long the system updates and renders at roughly 25 FPS or higher the system is usable perceptibly suitable for game play
This comes from the fact that a typical TV holds our attention because it does not fall below this threshold (i should insert a link to some research on this).
If the game updates and renders faster than that then few will be able to react fast enough for it to make a tangible difference, however hardcore / professional gamers push this statement to the limit every day proving that somehow some people can react faster than the average to state change.
Computer applications these days are variable based on the load being presented to them as it happens (so an explosion may effect frame rates / update speed depending on programming) which may have a positive or negative effect. Having a faster PC means I am less likely to be affected by the next guy in this situation which could give me a temporary advantage.
However when all is said and done there are so many variables in play that can take effect here. For example: The computer is typically running through refresh loops that are insanely fast compared to the rate at which network traffic is received ... so is there any gain to having a superfast pc that then can't update the network at the same rate?
What you tend to see with RTS games is that someone "hosts" the game by starting up the client on their pc and starting a "server" their interaction with that server is going to be orders or mangitude faster than anyone on a LAN or over the internet so games hosted in the cloud tend to have a better "fairness" to them in that everyone is interacting with the same internet latency (to some extent, ignoring ISP perversions).
But taking all of that in to the inner workings here Yes an individual command might be slower to place on a slower pc on a slower connection but the overall game state is a long running process that all users are within half a second of each other in seeing so for the big picture it likely makes little or no difference.
In short ... as long as the game meets that first point threshold of 25 to 30 FPS it really comes down to ...
If you see an enemy now or in half a second time are you more or less likely to issue the same command?
My thinking is ... YES you are so .. NO it makes no difference.
In an FPS style game however where the game state (perception of at least) changes so fast that may not be quite the same in that I may go left unless I see an explosion in which case I may go right ... my perception is shifted enough that it could effect my decision.
So the real question that should be asked ... What is the frequency point at which a game update affects the decision a user will make?
And that is a tough one !!