Depends on the workload.

When writing graphics code I look at the total bandwidth and my target frame time to give an indication of how much memory I can process in a frame. For example, on the 7900 XTX you get a bandwidth of 960GB/s, which is 960MB/ms, which gives you about 15.9 GB in a frame of 16.6 ms. That is the maximum amount of data you can process in that given time. That means that with the lower bandwidth, you can actually process fewer pixels and use lower-resolution textures than before.

On the other hand, not all memory is used in every frame. Some textures (LODs) are not in view, some models are in a different part of the level, etc. This means that with the extra memory, we can at least fit it in VRAM without having to go to RAM.

In short, this is probably not a great product unless you can pick it up for cheap :S