I'm thinking about Joplin Cloud vs. Dropbox -- I'd love to have the capability to use email-to-note in Joplin, but I also feel like Dropbox may be more secure from a redundancy point of view. Then again, we know that Joplin Cloud is hosted in Paris, but we don't know where Dropbox is hosted -- still, we assume that Dropbox is more secure...
Earlier today I tried synching with Dropobox and there were some unresolving synch errors... I thought of uninstalling Joplin but couldn't find any uninstall instructions..
It's possible that Dropbox is more secure than Joplin Cloud (they have way more resources than we do). But since they are more well known they are also a bigger target. Hackers are more interested in finding a zero-day there since they can get a bounty (or sell the exploit). A zero-day in Joplin Cloud would be worth a lot less, especially since most of the data is encrypted.
In general I'd say the web is more secure these days. Most "hacks" start with social engineering and Dropbox and Joplin Cloud are probably equally "vulnerable" to this.
We are going to add support for MFA soon which would make the service more secure.
From a redundancy point of view, there are daily backups of Joplin Cloud and the database is replicated in a different zone so as to be ready in case of a catastrophic event (such as a data center burning down, as it happens to OVH in France a few years ago). But also all your data is on your device and you can create a local backup of it yourself. That way even if there is a problem with Joplin Cloud you are sure not to lose anything.