Both the RTX 3090 Ti and RTX 4090 GPUs are probably overkill for gaming at 1080p resolution.
Both GPU’s should give you the highest frame rate you can get at a resolution of 1080p in most games.
=The RTX 3090 Ti is a great GPU for 1440p best nvidia rtx 4090 gaming as it can push 100+ FPS with graphics settings maxed out, whereas the RTX 4090 can only get 50-70 FPS with the same settings.
The RTX 3090 Ti will be faster than the RTX 4080 at 1080p because the RTX 3090 Ti has 2 more CUDA cores and 3 more RT Cores than the RTX 4080. The RTX 3090 Ti is the same price as the RTX 4080 but offers significantly better performance.
