I've examined (held in my hand) a Gatorskin and an Armadillo; I've used the Schwalbe Marathon Plus and the Panaracer Pasela Tourguard. Be aware that the weight can vary greatly among these different tires. The Gatorskin and Panaracer Tourguard are not that heavy (my Panaracer Tourguard 27 x 1 1/8 is around 300 grams according to the label that was attached to it). You probably get into the 400+ grams for the lightest/skinniest Armadillo, and the Marathon Plus is listed at 580 grams for the 700 X 25 size). I've had good (but limited) experience with the Panaracer Tourguard (I figure around 500 miles with no flats yet). I have mixed feelings about the Marathon Plus, it's the toughest-looking bike tire I've ever seen (it has an marked thickness from bead to bead, not just where the tire touches the road, and in the area where the tire does touch the road it has extra-thick layer of spongy material, I've read of some on this board that love the ride and some who hate the ride of the tire. I was initially turned off by the weight when I first rode it (using the Marathon just on my back wheel) and avoided riding the bike it was on. In time circumstances forced me to use it again on another bike and I just forgot about it being on my back rim and now I don't have a big complaint about it (keep in mind that I mostly ride for light exercise/pleasure and do some commuting, so bike/tire-weight is not my biggest concern).

I've found that I can ride just about any "thin-skinned" training/cheap tire on my front wheel without a lot of problems, but I need a beefier tire on my back wheel or I get a flat or two every 150-200 miles on my back wheel ( I weigh around 210 pounds). That is the compromise I make (a heavy tire on back and a light tire on front) so that I get most of the flat protection I need without adding any more weight to the bike than is necessary.