According to that first review, the FIR heater vest applies heat only to your back, and relies on your body to distribute the heat elsewhere, so that probably reduces its power use a lot. Some quick googling of FIR heaters has led me to think that the whole idea is generating as much radiant (FIR) heat as possible and as little conductive/convective heat as possible (duh). This makes sense, as it is probably easier to simply reflect radiant heat as you would light, to direct it at your body, than it is to completely insulate a conductive/convective heater, thus by using primarily radiant heat, less heat is lost to the outside world. So I don't think the heating elements themselves are any more efficient as far as total heat output, just that they produce heat in a way that makes it easier to focus the heat on your body, without requiring a ton of insulation, and thus less heat needs to be generated in the first place, so it's generating 35W of heat and most of the heat is actually making it to your body, whereas the wire heated vest might be generating 45-65W of heat total, but more is being lost so less of it makes it to your body. But, stepping back from the technicalities, I guess that practically speaking, the effective efficiency in terms of amount of useful heat (heat that makes it to your body) vs. energy consumed would in fact be better.
I would suspect that this special carbon - ceramic filament stuff they use for heating is probably not going to be anywhere near as cheap or easy to work with as wire though, if you can even find a place to buy it... and since info seems to be scarce on it, it might not be easy to make sure you use it safely...