- recovery records to be able to recover from mild bit rot
- support for more NTFS attributes and features (saving alternate streams, security records, turning hard links into links, etc)
- can do useful things with the archive attribute of files if you so desire (archiving only files with the attribute set, clearing the attribute after, optionally deleting them)
- better GUI (7zip UI is an incomplete WinRAR clone)
- when selecting multiple archives, you can extract each to their own subfolder with a single command
Overall WinRAR is the much more solid archival tool. If all you need is something to decompress archives WinRAR isn't too different from 7zip, but has a slightly nicer UX.
Not a huge issue, but I can see someone who installed 7zip, think didn't worked and then install WinRAR.
“Using Recovery Record slightly increases the size of your .rar files, but it helps to recover data should your file become corrupted by a virus, bad disc, etc. The larger recovery record allows you to restore a bigger damaged area, but increases the size of the archive and the process is slower."
The floppies often had issues, so a single corrupted byte would normally corrupt the downloaded files (especially images and binaries) but with 10% or 20% of recovery data written in a non-damaged place, it could manage to un-rar.
If you're curious how this works: say you have some data like below:
10001100
11001010
11001010
01001010
10001100
11001010
11001010
01001010
You can calculate a sum of each row and each column, mod 2, and store it somewhere. When a single bit gets flipped, with the extra data (assuming the recovery data itself is not borked), you can calculate exactly which bit got flipped. (You can also calculate other kinds of extra data which can deal with more complex bit flips).Also, from what I read in the comments and tweets, a lot of people who bought the licence did it more as a "thank you for all this year where we could use it for free"
And finally, as it was a promotion, the guy(s ?) at the end of the email adress had to make the links one by one and didn't had enough times to reply to all demands. If they'd planed it, with a dedicated page, I think the result could have been huge
Or doing the opposite, selecting many folders and telling winrar to create a .RAR file from each folder.
Etc.