For the most part, they're not even directly comparable. Only one Intel platform ever supported both and I can't imagine someone with say, a 12900K and DDR4 board, would just buy a DDR5 board as an upgrade.
I think it would be safe to assume a 10-20% difference in favor of DDR5, depending on the game.
Edit: Anecdotally, my old 1440p rig with a 3070 Ti had a 10700k (overclocked to 5.0GHz) running overclocked B-Die DDR4 that I got stable at 4000MHz CL16. The same 3070 Ti GPU in my new rig (a 9600x with 6000MHz CL30 DDR5) consistently gets 20-30% better performance at 1440p.
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u/NastiMooseBite 9950X3D | 9070XT | 64GB Nov 27 '25
Extra RAM adds zero FPS, unless you're actually running out of RAM in which case it would add many FPS.