Unless you have a high speed upload connection (there are many options, usually expensive) online backup is a slow proces, with associated long times to upload and download. It should be used as a "last resort" resource in case of major disasters. You need to have additional local backup & redundancy options.
A good excercise is to think in relation to business/operations continuity before deciding on a solution. Think about severity of possible events, likelihood of it happening, best solution and cost (which should include how much time is acceptable to you before restoring to full capability).
- Major: fire, flood, earthquake; Likelihood: low (well, depending on where you live or the location of your facilities); best solution: Online/offsite backup, cost: many options, but you have to balance the cost of operation vs the cost of waiting for weeks or months before restoring your data
- Medium: disk failure; likelihood: high (in my experience); best solution: Reduntant data arrays (I don't recommend Raid 5 BTW), Cost: low
or data corruption by virus/other issues: likelyhood: medium; best solution: local backup in media that is not permanently connected to ensure data corruption did not reach it.
For major events consider also how are you going to recover your software, especially if you are running discontinued/unsupported software, which you may not be able to reinstall. For this a clone of the O/S disk, separate to the other backups will help too.
In addition you should separate backup sets, as the typical case is part of the data does not change and does not have to be updated frequently, in contrast to work-in-process files that you need to backup each time they change. It is very likely that you'll need to restore the work-in-progrees data as fast as possible and you can wait a few weeks before completing the restore of your archive data.
One note about online backups and some specialized tools: in addition to compression, they also perform data deduplication (in a very simple way: looking for similar blocks of information and storing them once) increasing notably the performance and reducing storage space required. It is recommended to have also a local non-deduplicated backup set just in case.
Remember: There is not such as thing as too many backups