Richard Nisley at BPL has put together a lclo comparison of various different insulating garments here (subscription not required). The chart is focused on Mont-bell garments; a good decision because its garments are warm for their weight, weigh very little for insulating garments and are reasonably priced. As it has been said for sleeping bags, your general feature options are lightweight, warm and cheap - you can pick two but cannot have all three. Montbell insulating garments are an excellent balance between these three factors. As a bonus, Mont-bell has a wide variety of insulating garments.
Like many, I have been waiting for a similar chart for a while. Also like many, I have not taken the time to truly sort out the volumes of data available on various garments to figure out what temperature each garment is capable of dealing with. I would gladly support entering and continuing this chart into BPL's Wiki to assist persons in researching insulating garments.
The most interesting find (and forum posts concur) is how significantly warmer the MB U.L. Inner Down Parka is over the Thermawrap parka despite the Inner Down Parka weighing five ounces less. The chart also demonstrates scientifically the difference in warmth between between the Thermawrap Parka and Jacket. The Parka uses 80 g/m^2 of Exceloft and has a hood, while the Jacket uses 50 g/m^2 of Exceloft and lacks a hood. I prefer the Parka because of my preference for hoods. I would only use the jacket is I was using it as a true inner insulation layer, such as under a hardshell and a larger insulating parka.