(Before you read this, I am open to debate encase you also have experience/worked on games and have done your own benchmark tests.)
I was reading the thread http://forum.facepunch.com/showthread.php?t=1494436 about what kind of fps the author would get with his build and someone stating go for i5 instead of i7 and get a better gpu. What a lot of people don’t realize is that the main reason rust lags on a highly populated server, is because of the many low poly objects with colliders in the world(drawcalls). The main reason the game is gpu intensive is because its filled with a shit ton of speedtree’s + grass (the structures do take some gpu rendering).
I rebuilt legacy’s building system (I have a good idea how they did it and realize why the collider limit is such a problem) in unity awhile back and confirm the lag of having many buildings even though they are made of very few poly’s. This is an issue steming from to many drawcalls/colliders and its related more to the cpu so having an i7 for rust should be beneficial. I can’t think of a game that has a similar building system in place other than The Sims and even then its only 1 house you’re seeing instead of an entire village in an open world. Rust really isn’t unoptimized, its just pushing the envelope when it comes to player housing and people tend to compare it to the usual games we’ve been playing all these years.
Cinebench R10 32-Bit (Single Core)
Core i7 4790K 8,785
Core i5 4690K 7,619
13% increase in performance
So, in a brand new world with no buildings and tons of tree’s, a gpu will be more important. In a heavily populated world with 1000’s low poly lego brick like structures with colliders attached churning out ungodly amounts of drawcalls, a beast cpu is going to help greatly.
If I had to choose though, I would still pick a high tier gpu and a mid tier cpu because that’s what almost all games benefit from the most. Just remember if you want the best performance in rust, you’ll want a top tier cpu as well. Possibly more so if all you do is play rust on populated servers, but I doubt that. It’s a tricky balancing act because the requirements change as the server progress’s.
p.s. Get shit tons of ram. 4gb is not enough, 8 is minimum, and 16+ is what I recommend + its dirt cheap now.