Two layers of Heavy Duty foil together will measure 1.88 mil thick vs. 1 layer of Pitmaster's Choice measuring 1.40 mil. That's 34% thicker than Pitmaster's Choice. I don't know if two thin layers of foil have the same "structural integrity" as one thicker layer, even if not quite as thick.
Reading the comments on Amazon, some people prefer the durability (less tearing/puncturing) of the thicker material and ease of single wrapping vs. double wrapping. But it comes with a price. Not for everyone, obviously, and probably something I won't buy again.