They seem to be close? The RX 9070 is the 2nd most efficient graphics card this generation according to TechPowerUp and they also do well when limited to 60Hz, implying their joules per frame isn't bad either.

Efficiency: https://tpucdn.com/review/gigabyte-geforce-rtx-5050-gaming-o...

Vsync power draw: https://tpucdn.com/review/gigabyte-geforce-rtx-5050-gaming-o...

The variance within Nvidia's line-up is much larger than the variance between brands, anyway.