Well it depends. if you want them easily accessible you might want to get a cd-writer. but if you have ALOT of stuff that you just need for personal use you might wanna get a HD since it will hold tons more and be alot faster to write too
I think it comes down to this...If you plan on continually changing or accessing the pics/media then consider the HDD (faster all the way around). If you're looking to archive or put them in a "safe place" then consider the CD or even DVD. The HDD is faster and easier, however it can become corrupt more so than the CD and possibly un-recoverable (backups, backups, backups). Once you burn the CD/DVD and verify the data, its there until you physically harm the media source beyond the point of reading/writing.