It has been my experience, and I can only speak for myself, that I have found it best to carry more smaller cards, instead of a few large ones. While you may need to change cards more often, at least if one "dies" you do not loose all your shots.
Also because the D3 has the duel slots, it is a bonus to have and I am more confident that while one may play up, I am reasonably sure the other card won't. I do make a habit of only formatting the memory cards in camera. I do copy and paste from the card, confirm file integrity, before putting the card back in the camera for the camera to format it.
I don't cut and paste, I only ever copy and paste. Once again, the chance of the computer crashing, a power failure or something like that has never happened, but I always .... "Err" on the side of caution.