Magnetic storage will likely last longer, and as it is a much older tech, is less likely to have firmware bugs and other problematic surprises. Plus, as you can see on diskprices.com, the cheapest medium per TB remains magnetic storage.
Then there are tapes. The drives sure cost a hefty sum, but if you have loads of data to backup, this is likely the cheapest option.
Finally, optical. Optical is great in the sense that is is physically a ROM, so data cannot get compromised by mishandling or other staff mistakes; but it still can have issues with the reflective layers peeling away from disks.
So, in the end, I would personally not recommend using SSDs for data backups, out of precaution. Sure, SSDs will likely retain all data just fine for years to come, but I want to be able to store data for as long as possible, with the peace of mind that only magnetic storage will afford me. Plus, if your data is worth backing up, it is worth whatever extra price or effort you will have to do with.
As for the other options, well, they all have their use case, but I don’t see much advantage for them in the general use cases. Just make backup copies of your data on magnetic drives, in a few physically different locations, with proper access control.