2 sticks. I think it’s how the CPU distributes all the information over the data lines going to the ram. Four sticks can cause instability. i’m not even sure why they have four spots for RAM on gaming motherboards anymore. Absolutely everyone recommends just two.
if you do a search yourself it actually gets pretty complicated. Because sometimes four sticks are better for certain situations. it not only depends on your set up, but also the games. But here is a quick article right from Corsair.
It’s also recommended that if you go from say 2 x 16 to 4 x 16 then you should buy them as a kit and shouldn’t mix a match. As I said, it gets complicated it may or may not work for your set up with the your games. But would work with the next guy’s set up with his games
As another had said, it depends on your individual situation. If you’re not over clocking, 4 is better. If you are working on projects that require more memory over speed, 4 is better.
But if you are over clocking, 4 can be a hassle to get to work and there are fewer kits available to support and is more volatile. (Check a compatibility list for your mother board and CPU). Or if you don’t need a whole lot of RAM, 2 would be best.
Like I have a gaming system that uses 4 but I use it for other projects. But I’ve also a 3d rendering system that uses 8, those aren’t over clocked and memory is more vital than speed.