The rules are in my Passport FAQ
. The passport card has many restrictions, the biggest of which is that it is worthless if you need to fly in or out of the U.S. The process for applying for either is the same, so why go through it and settle for the lesser ID? I plan to get both when my passport renewal comes up.
Please don't post the same question multiple times in different messages. Since you already asked this in another post I'll close this one.