This relates only to the power of the standard board. Most important is the maximum voltage that you can set. This will be 1200mV for both cards, so that the actual consumption is not much different.
Since both the 6950XT and 6900XT LC have an XTXH chip (a high-quality version of the regular chip), you can set new limits for both wattage and voltage with a tool like MorePowerTools. Then all of a sudden the card’s temperature control becomes the main limiting factor.
Out of the box, you have a good chance that the 6950XT will perform a little better, but if you start with these kinds of modifications, I think the LC version does better because of the more efficient cooling. With these cards, better cooling usually means better performance.

The difference between the “regular” RX6900XT cards with an XTXH chip and the 6950XT is the memory speed. Since you usually can’t clock more than 2150MHz with the 6900XT, you can achieve much faster speeds with the 6950XT memory chips.

There is hardly any practical use, but you do get brutal scores from TimeSpy in 3DMark.

So if you already have a 6900XT to play with, it makes no sense to buy a 6950XT than to buy a 3090Ti if you already have a 3090.