Yes, mine are heavier than a regular felt pad. The don't weigh a TON or anything, but they are definitely heavier than just felt. I am also a heavier rider, so I think about things like that, but I use them anyway because I figure they make up for the extra weight with protecting the horse's back.
Now it seems like I have heard the newer ones may be lighter, but I am not for sure on that. Mine are several years old and I have never felt a newer one in person. It just seems like maybe I have heard that they are, but I could very well be mistaken.
Just don't get anything with memory foam. My friend who sold me her old Impact Gels bought a couple memory foam pads to replace them, I think they were Classic Equine, which should be a good pad, but the memory foam layer must collapse because they condensed and left the imprint of the saddle in the pad, permanently, in just a matter of months. She was very disappointed in those. Now she uses 5-Star pads. They are really nice too, but I am not convinced they are better than Impact Gels. And they are just as expensive if not more so than the Impact Gels. And they are solid wool felt. For the money, I don't think you can go wrong with the Impact Gels. The 5-stars are lighter weight though because they don't have any gel inserts.