In reply to GHawksworth:
I agree with this. The Halo jacket is almost 20% warmer, given its fill weight and fill power. Also, the Microlight is close to being 40% heavier! (my Halo is a bit heavier when compared to official specks, but still 100 grams lighter.)
I own the original Microlight, which I like because of its tougher exterior shell and slightly better fit for a medium build, but when weight, packed volume, and warmth are an issue, for long hikes or belaying, I take the Halo jacket .