The Xenon is going to be 3 oz. lighter, mainly because of the lighter weight insulation. The Xenon is also going to have a much more trim fit to it. The two jackets both have the high quality and high performance features that Rab is know for. The Xenon is just a more high end version of Inferno which is most easily scene in the price. However, the Inferno will in fact be a bit warmer. The Xenon is more for performance and the Inferno is more of an all around jacket.