system
A chat on subreddit /r/pcmasterrace
human
How significant is the performance increase?

For example, would you still be better off running 1x16GB instead of 2x4GB?
gpt
You can find benchmark comparisons on single vs dual channel, and speed benchmarks. The short is, single channel vs dual channel is a large increase in the smoothness of a game, specifically due to better performance in the low-FPS moments. Essentially, less stuttering. 

Gun to my head, I'd rather have 2x4gb assuming all else is exactly the same. I'd just shut down background processes when gaming. You should run 2x8gb though over both.