recently I picked up a New Balance Fugu Down Jacket jacket on the gearswap.
Just to test the warmth for weight against my Western Mountaineering Flash XR which weighs the same. I did a short unscientific test.
I put the coat on and sat for 30 minutes with a fish tank thermometer in my cell phone cover and then in my chest pocket for each jacket. The Western Mountaineering had a temperature of 78 degrees. I was just lying on my bed at home. The New Balance Fugu Down Jacket had a temperature of 84 degrees.
Not a good jacket to charge up a hill in, but I can't wear jackets with a pack on, I just sweat too much but once I get to camp and I'm just standing around then it's nice to be warm.