32GB wins for the 7800X3D.

Get the 32GB kit. That CPU’s 3D V-cache makes RAM speed a lot less important than it is on non-X3D chips.

The 7800X3D basically shrugs at memory timings in most games. You’ll see maybe 1-2% difference between 3200MHz and 4000MHz. What you will see is running out of memory when a game plus Discord plus a browser eats 18GB. 16GB is already tight in 2025 for heavy multitasking or modded games.

Only exception is if you’re doing pure, locked-in competitive gaming at 1080p and nothing else runs in the background. Even then, I’d still take the 32GB because future games will want more.

Don’t overthink this one. Capacity now, speed later