I will be ordering pad and carpet in my basement in the next couple days... When shopping, I have been told to be sure to get a pad with a moisture barrier, and then I was told not to get one with a moisture barrier.
The reasons for a moisture barrier:
1) To protect the pad from any moisture from the concrete.
2) To protect the pad from spills on the carpet.
3) To protect the pad when the carpet is steam cleaned.
The reason why not to get a pad with a moisture barrier:
1) The moisture will be traped between the cncrete floor and pad, and between the pad and the carpet.