In this part of the world, it is not a given to have internet access, let alone fast internet access. Speed or time it takes to make a backup and retrieve those files from the available cloud solutions is often overlooked.
8GByte pen drives don't cost much, are usually fast in storing and retrieving of data and retain data reliably without someone peeking when such drive(s) are stored in a rented safe/storage box in a bank. You have full control over the amount of encryption you apply to the data on those drives.
Cloud solutions are more convenient, but will be released to law if requested firmly enough by local or international law and always under attack by people who want to gain money and/or power over your data. You have (much) less control over the amount of encryption you apply, depending on the provider of the cloud solution you selected. And, of course, when there is no internet, you cannot make a backup or retrieve data from your cloud solution provider.
The "no internet" part doesn't have to be your fault or the the fault of your cloud solution provider. Connections can be disrupted by something as simple as a construction company accidentally destroying the cable(s) or other infrastructure of your ISP. If you are in a muncipalidad that firmly believes in keeping electricity and communication cables on poles above the ground, your internet connection can be disrupted by (electrical) storms, accidents, a car/truck hauling a load that is a bit too high or plain simple gravity.
In the Netherlands all cabling is put underground (and properly mapped) making any kind of network very reliable. So over there the cloud will be a fast and very reliable solution. Combined with its convenience a no-brainer for most.
However, in Paraguay where I live now every cable is above ground. Even fiber cable connections (especially the last section to the house of the customer) are not put into the ground. This makes internet connections unreliable. Connections are more expensive too and paying even more for a cloud solution provider that might or might not work. No, for me the convenience does not make up for lack of reliability and related costs. Over here, I am much more inclined to use pen drives or a portable hard disk for backups and store/retrieve those physical devices myself either on-site (in a home vault) or off-site.
The whole essence of a backup is to be able to reliably retrieve data from it at the moment it is needed. If that isn't the case, you may delude yourself by calling whatever you have stored in the cloud a backup still, but it really isn't.
You stated that the info you want stored is 'extremely important'. In that case, don't be fooled by the convenience promised by cloud solution providers, but make sure that they, your ISP, the infrastructure and yourself can deliver on that promise. If you have doubts, use a pen drive or portable hard disk for backups.
Either that or reduce the importance of the information, of course.