purchase the 2 person ones, they are just a fraction heavier (and a tinier bigger folded up), but the extra size is well worth it imo
compared to your run of the mill "space" mylar blanket- no comparison, Heatsheets are much better
Agreed on the advice for purchasing the large ones. Having played with both, the biggest selling feature on the heatsheets is that they are tear proof. If you nick the mylar one it instantly begins to tear and pretty soon you have tinsel. Basically, the AMK ones behave exactly like a heavy duty garbage bag. Rather than tear, it sort of stretches just like a garbage bag does. In fact as somebody pointed out in another thread, the barrel bags are perhaps as good as the heatsheets at a bargain except you don't have the coating on them. In some cases, having a bag formation rather than a blanket is more desirable. Really depends on anticipated uses.
Another selling point on the heatsheets is that they are packed with survival information on the orange side. Lots of great advice written on there from shelter building to medical and signalling advice. Its a very well thought out product.
Like all blankets of this sort, they are best when you purchase them machine packed. Once you open that baby up, you'll never get it to fold as small as the original was. However, I have re-used my opened one up many times on different things and I can usually scrunch it back up into a ziplock sand which bag. Keeping in mind that it is basically a sheet of plastic with a reflective coating on one side and orange on the other, it really is a great piece of kit. If you take the bother to buy one, then you might as well buy three or four and shove them in the BOB, car etc.
For a versatile tarp, I think the casualty blankets are far superior still. They are much, much heaver and bulkier but serve as a great ground cloth, real tarp.
Here is an old video I did using both a heat sheet and casualty blanket to work up a bowdrill in the snow. The blankets don't show up until 2.18 min, so you can skip to that part.
[youtube]BtSBMefrtkU[/youtube]