I have an external HD attached to my media center, and it backs up everything (recorded TV, media, applications, etc). With Windows backup I have to keep an eye on the space left and go in and delete older backups manually. If I forget I don't get a backup until I do that again (and I have to do it probably once a month).
Does Acronis automatically delete older backups? I really like that feature of Apple's Time Machine. As long as I remember to plug the drive in periodically, it just keeps backing up stuff and removes the really old stuff automatically.