Thanks very much for that well informed comparison!
I have the micropuff and I am generally happy with it. Its advantage, to me, over down is its ability to handle some wetness while doing camp chores, as it is synthetic. Also, in the event of catastrophic wetout of my down sleeping bag, it is my back-up. IMO the chance of this is small since I use POE's kayak style dry bags.
However, the micropuff's disadvantage is its bulk when packed compared to a down jacket. Now that I know the Montbell is somewhat warmer with excellent DWR .... temptation strikes!