I've noticed a large difference in the price of SD Cards. Is this because the more expensive cards contribute to a better picture/video. Some of the cards say they're "faster", is this meaning transfer rate? I use a Jazz HDV 178 and it's a 5megapixel camera... should I be purchasing the expensive SD Cards? Quite frankly, I tried a very cheap card today, SanDisk 2gig, Class 2( whatever that means). I saw no difference in the pics and videos on the highest setting as compared to a Panasonic 4gig, SDHC, Class 4. Any thoughts or recommendations appreciated. Thank you.