You need both. Use the Dell local backup to create Recovery Disks. Then use Windows Backup to backup your files to EXTERNAL media. Do not use the D partition on the boot drive. You need a thumb drive or external hard drive for backups. Windows will allow you to use the D recovery partition but do not use it for anything. Windows doesn't see that the D drive is not a drive at all. Read the directions for creating disks Here.
Just received my new Studio 15. Looks like two backup systems included:  Dell's local backup and Windows 7 backup and restore.  Looks like both will create images for recovery and backup data files.  Which should I use? And why is there a Dell program to do this if Windows already has the capability?   Thanks for any help anyone can provide.    
Dell Backup or Windows 7 Backup