They’re quite different. In fact, I don’t think there’s any real shared code between the two. I made The Wall first, trying to make a limiter that can be pushed it hard as possible and remain transparent. It uses a combination of multi-band, multi-pass limiting and clipping to try to shave just a bit off at each stage.
Big Clipper is more of a way to blend clipping and limiting together so that you can control how transparent it is. But it’s not specifically designed for transparent loudness maximization, it’s designed to be heard, but in such a way that you can control how much it is heard.
I could probably take some of the things I learned from making Big Clipper and apply it to The Wall to make it a bit more transparent. If/when I do a version 2 of The Wall, I’ll probably do that. I’ll probably end up doing a version 2 of Big Clipper as well to make it a bit easier to use and understand.