The massive downsize of zip is that each file is compressed individually, which means very poor compression. Overall the compression rate is significantly lower

The massive downsize of zip is that each file is compressed individually, which means very poor compression. Overall the compression rate is significantly lower, same with an attempt to decompress it all. It's only useful for random reads of few select files. Tar -> read, skip, read, till you find what you need, compression doesn't change much, as most stream compression algorithms have a flush method.