14 bit capture has about 16% more information than 12 bit. If you want the best possible quality, shoot 14 bit. If you then need more capacity than 400 pictures (I only get 320 on the D3) then get more cards. I carry 6 4GB cards and even on expedition last year to Alaska for a month, they were plenty and I had no means of downloading until I got home.
If you select the lossless compression, you will lose no information but gain a little capacity.
Only you can choose. I shoot lossless compressed, RAW at 14-bit and use 4Gb cards with the second slot on overflow.My cards are years old now and still perfectly good. There are certain things you need to do to ensure long card life:
never delete in camera, instead be selctive about what you shoot - either bite the bullet and shoot it anyway, or be more selective. The reason you shouldn't delete in camera while shooting is because the card over writes and that is one way to get corruption.
The other thing is to format the card every time. This does mean that you cannot recover any files afterwards with rescue Pro or whatever rescue package you use, so only do it once you are certain the images are safely downloaded and backed up.