If you or anyone you allow access to the data need easy access whenever and almost wherever, then go cloud. Just make sure that you have other means of backup.
Backup leaks cannot totally be prevented. The cloud service team will probably have access to your data and you have no control over what they do. That is why I said you can personally apply encryption to your backup before storing them on cloud. The current strongest encryption algorithms will probably take years if not decades to be cracked by the strongest computers in the market. And you can use a combination of these algorithms. If you can't trust these algorithms, what can you trust?
If you don't need access to the data on the go, don't bother going cloud. Unless of course if you are an enterprise and require professional management of your data.
Strong encryption, at your end before the data is sent into the cloud, is the key (excuse the pun). There are cloud storage services which will encrpyt while passing the key into your possession, but it's easy enough to do yourself anyway.
That said, if it is 'extremely confidential' then perhaps you should be rethinking whether you want to entrust it to a third party at all.