Decisions decisions...I'm looking really hard at either the MH Compressor or the MH Phantom Down Jackets, and I was hoping you lovely outdoor enthusiasts could lend some advice. The main uses would be winter camping/hiking/backpacking, winter/cold-weather climbing, mountaineering, and hanging out on backporches in the cold. Any thoughts on which might be better? Or if I'm looking in the right direction? I would really appreciate any help I could get.

You are looking in the right direction for sure! The Compressor jacket is a tad lighter, plus it stays warm if it gets soked and the Compressor is a tad longer. The Phantom is going to be warmer but if the down gets wet the jacket losses some warmth. They have about the same features and the Phantom packs down a little smaller. If you plan on needing you jacket for wet/soggy and cold conditions, go with the Compressor - it kinda sounds to me though, that the Phantom is going to be the better choice for you.

I'm in the market for the same thing. I think you need to base your decision on how well you can handle your down clothing. Down in general compresses better, but it also loses all of its insulating property when it gets wet - and this includes when it wets out from your body sweat as well as from external moisture. Many guide services recommend a synthetic insulation jacket for layering, and then a waterproof down parka that goes over everything (including your hardshell) for really cold conditions, typically when summiting. I have a Patagonia down sweater that I really like, but for mountaineering I want the extra insurance that a synthetic jacket provides. These jackets generally seem to be an adequate (and less bulky) replacement for fleece jackets, with the actual warmth obviously dependent on the individual jacket. You will need to decide up front how you want to use the insulated jacket in your clothing system and then make decisions based around that.