Either will work, but they work slightly differently:
Incremental - You take a full backup, next week you make an incremental backup, and every week thereafter. Each incremental only stores the bits that have changed that week. To restore however you need the full backup, and every incremental backup since. (To restore to a point of time you'd need the full backup and every incremental up to that point)
Differential - You take a full backup, every week you make a differential backup. Each differential backup stores everything that has changed since the full backup. To restore you only need the full backup and the latest differential backup. (or to restore to a different point of time you need the full backup and the differential from the appropriate point of time)
The risk with incremental is that they are dependant on each other - if one backup in the middle is corrupt or accidentally deleted then you have no way of restoring past that point. The advantage being that they are done quicker, and take less space - only storing the changes since the last incremental.
With either though you are probably best off still having regular full backups, and as with everything test that you can actually restore your backup before you need it.
