The more I used 7-zip
, the more I liked it. It compresses much better then for example .zip, and that's what it is good for. But I wouldn't recommend it for doing backups and similar. If there is one byte damaged, you usually can forget the whole archive. For .zip, every file is compressed separately, so it isn't that severe, if something goes wrong, it is usually possible to repair the damage or even work with it.