Each camera manufacturer uses specific types of memory cards. Smart Media is a dying (probably dead) type of card. xD is used primarily by Fuji or Olympus, Compact Flash was the defacto memory card for high end cameras and is still used, although some camera manufacturers are switching to SD cards, SD cards are the most common cards now, and Memory Stick Pro is used mainly by SONY. There is no best card. Once you feel that you are at end of a photo session, ie. a wedding, this years Christmas parties, you should dump your card to your computer's hard drive. These files should be backed up to either an external hard drive or preserved on a CD or DVD. This is best done when you can fill the CD or DVD (to minimize the number of backup CD's/DVD's in a backup location.