Both are good choices. If I was unable to get the factory cover at a reasonable cost, I would have definately bought the Advance cover.
Here are the basic differences;
Factory Cover-
Apx 75lbs, Strong enough to stand on, Can be keyed to match vehicle, can open and close tailgate while cover is closed.
Advance cover-
Light weight, low profile, much lower cost.
Which ever one you choose, you can't go wrong.
Edit;
If you choose a factory cover, I would also recomend the easy-lift from Rich Lunder.