LZW just doesn't compress that well. In LZW you only can use a dictionary built gradually from length-limited scraps of the previous data, but in LZ77 you can d

LZW just doesn't compress that well. In LZW you only can use a dictionary built gradually from length-limited scraps of the previous data, but in LZ77 you can directly reference any of the previous data of any length (within implementation limits).