Speed and memory
In our performance index the GeForce RTX 3070 scores 37 and the GeForce RTX 3060 Ti scores 33, which makes the GeForce RTX 3070 about 12% faster. That is a visible but modest gap, usually 5 to 10 fps in a game that runs at 60.
Both cards have 8 GB of video memory, so memory will not separate them.
In our estimates for popular games at 1080p on High, the biggest gap is in Cyberpunk 2077 (96 against 86 fps), and the smallest is in Red Dead Redemption 2 (124 against 112 fps). Games that are light enough to run above 200 fps on both cards show little difference at all.