An online backup service's speed depends on how quickly it can encrypt, compress, and upload files to its servers. This should be of particular concern if you need to back up (or restore) a large amount of data. A high-performance backup service also minimizes its effect on network and system resources. Make sure to check out our speed test results in the review of any service you're contemplating using. Backup speed should not be the sole determinant of which online backup service you use, but fast upload speeds can certainly make initial and subsequent backups less disruptive.
The iDrive service comes with backup clients for nearly every PC and device, including Windows Phone—a rarity these days. The company provides additional storage for syncing all your devices and PCs, allows sharing of files with anyone, and has the ability to back up to a local drive. The company also has several affordable pay plans. For all the details, read our full review of iDrive.
Since you're probably going to be paying for a backup service for years, cost is an important factor to consider. All the services rounded up here are subscription-based, but they partition their features and fees differently, so it's worth comparing plans closely before committing to one. Most construct pricing tiers based on the amount of cloud storage included, however, or by the number of devices you can use with an account. A few services offer permanent free accounts, but those plans impose paltry storage limits or restrict key features to the paid versions. Watch out for file-size upload limits as well.