If it is just for storage and you not writing much don't worry buy cheep.

If you copy date on a off as I do class 6 and above. I have found that not all class 6's are equal. The brand name is usual faster and natural more expensive. So if you subscribe to the notion that time is money you want the higher class.

I suggest reading the reviews on amazon someone inevitably has done a direct comparison between apples and "apples"