Cost is a major factor in what you buy. A rare SVC will be worth a premium whether mint or used. Some of the best examples in my collections are used ones. However, there's still something special in a MINT item. Although SVCs and the SVC market are still brand new, we have available, today, items that will become the rarities of tomorrow.
Card Readers are available to check the Balance remaining on most major SVCs.
Inexpensive models often have contacts that scratch the surface of the chip as the card is pushed in. Better models have retracted contacts that are engaged by pushing a button, after the card is pushed in, and do not scratch the chip to read the balance. SVCs should be stored in protective devices to protect them from from scratching, staining or discoloring. Presentation Folders should be protected from bending and tearing. Albums are available to display and protect your cards.