I care for neither.
-7900 XT user, it's the reason I went with Radeon this time around.
I have done a video showcasing the huge disparity between an AIB card like my ASUS TUF model and setting it to Radeon MBA clocks with 2.4ghz boost, the power usage difference is pretty insane, and whilst yes the under volt helps, it is the clock speed drop that effects it the most, since the driver is made to push power if you mess with the power slider, however as seen with Heaven 4.0 which is what I test with for stability, the clock speed and limits can be hit without touching the power limiter even with a -10 power limit suppression.
If you follow what I do, then be sure to test it in very hard games that push the GPU harder.
Otherwise, it's about as good as it is going to get with a Radeon, still my card runs 320w stock, 240w is a substantial drop with around 7 FPS on average loss. Coming from a 1440P 240hz user.
For the 7900 users out there, efficiency of 7900 XT when controlled.