Everything on archive.is is on archive.org. I would say 99% of stuff.
If archive.is goes down we have webcitation.org, etched.page, ghostarchive.org, webrecorder.net, etc....
If archive.is goes down we have webcitation.org, etched.page, ghostarchive.org, webrecorder.net, etc....
4chan has archives dedicated for that site anyway (Warosu, etc.).
Given how a LOT of the stuff today is behind paywalls and Archive.today breaks through most of them and Archive.org doesn't, your "99%" figure is way, way off when it comes to popular stuff.
Anyway, I donate to both the Archive.today and Archive.org. They're extremely valuable to me. I feel like Archive.today is in a dire situation when it comes to funding so I donate more than double to them each month.
If you're able, please donate to these sites. They are running on fumes. And take a look at my profile for a list of other orgs to donate to.