Never trust a single point of backup on an Android phone, especially one controlled by a carrier. I make 4 different backups of my phone before doing any migration or factory reset. I use SMS Backup and Restore for text messages. I backup Contacts by saving all my contacts as a VCF. And then I use Lithium to make a full phone backup (although it didn't restore very much when I tried it).
You can connect your Galaxy S4 to your PC and copy all the photos, music, videos, etc. yourself. You don't need a 3rd party or cloud service to help you with this.
There is no one service or app that backs up everything.