I've been using 7-zip for a long time now. It quickly became my favorite zip/unzip utility. It's quick, easy to use, opensource, and best of all, FREE.
A few months ago I worked on a project to gather and zip log files from numerous S3 buckets and archive them in another location. Initially I specified the "zip" compression method and the files were stored with a .zip extension. One day I was experimenting with the log files and realized that using "7zip" compression, while it took a little longer to complete, the files were considerably smaller. In my case it doesn't really matter how long the files take to compress, but I want them as small as possible since I'm using an S3 bucket for archival and want to spend as little as possible.
As an example take 30 files for June from one of my buckets. The files were 5.6GB in total size as ".zip" files, but only 3.6GB as ".7z" files. That's about 35% less! Granted, we are only talking about a few cents a month here, but as I said earlier I have several buckets and keep several months of logs from each bucket, so it adds up over time. Definitely worth the additional processing time to use "7z" compression.
Take a look at a file-by-file comparison: