So, I honestly am being careful to not wear these 2 jackets too much, because I'm planning on sending one back and don't want anything to happen to it. But my impressions are:
Down Inner Parka:
Feel: Unbelievably light, like putting on a cloud...seems like magic that it can keep me so warm with such little material
Fit: It's fitted (which I like, as opposed to some other down sweaters) but I can easily fit other layers underneath. I'm 5'10"/150 and the length + arms are perfect and the chest fits fine (though another 10-15 pounds on me would make it perfect). Easily fits layers underneath and shell on top.
Look: Actually, this was surprising a point of contention. The royal blue is pretty shiny (and reading some reviews of other colors says the same), to the point of looking over the top - fine for camping, but not as good for around town/out to dinner. Not sure how this compares to the Ex-light. Also, my wife says that the vertical lines on the fitted style, in combo with the logo being at the bottom of the jacket, make it look sort of like a girl's jacket (not sure I agree, but there you go). Neither of these things is a dealbreaker, because I'm generally after function more than style, but I do want to feel good about wearing the jacket around town.
Function: It has only gotten down to around 25 here the last few nights, and this jacket works fine at those temps, particularly when I put up the hood. This was a test of sitting on my porch with just a base layer + this jacket (no hat or gloves even) for an hour. I wish I could test it at lower tempatures. I certainly deal with the cold pretty well, and I really want to know how low I can go with this. Packs up into a softbell - I can definitely see throwing it in my pack during any season or condition as a result.
Alpine Light Down:
Feel: Definitely light, but after holding the down inner, can really feel the 7 oz difference in weight. Again, feels really good wearing, but feels like you're wearing a coat, not a cloud. That being said, it also feels warmer because of the extra weight/down.
Fit: More fitting than other down jackets like Patagonia down sweater, but not as fitting as the Down Inner. Size/fit are about the same as above. Fits fine over layers, and under my shell (though I look a bit puffy in the latter case).
Look: I got the black, and it looks pretty good. Not nearly as shiny as the blue down inner (though I wonder if the other alpine light colors are). I also like the more traditional baffle design, and logo on the chest. The jacket is certainly puffy, but not Michelin Man level. I do wonder if I'll wear this around town as much as I would the Down Inner style as a result.
Function: Totally comfortable down to 25 sitting outside - again, felt a bit warmer than the down inner, but hard to tell since I was comfortable in both. As with above, I wish I could test lower temperatures, and layer combinations. Packs down pretty small, but only to about twice size of down inner - still light/relatively packable, but I begin to question ease of throwing it in my pack at any time.
I like both jackets, but I'm concerned about the closet test on the Down Inner because of its shininess to wear around town or out to dinner, and the Alpine Light Down because of its puffiness for non-really cold days, and for general usage. I really wish I knew how low I could push the Down Inner, esp. with layers (base + fleece + down inner + shell) because I seem more inclined to want to pack up / wear it all year round. The Alpine Light Down seems like something I'd wear primarily camping in dead of winter, and other than that, I wouldn't need that sort of warmth.
Still no decision - I think that if there was a black down inner parka (or similar non-super hero color/sheen), I'd keep that and see how low I could push the temps with my layering system (my hands are what I always have issues with, not my core). In that case, I'd buy something heavier to augment it, like the Alpine Light Down, as needed. The one pro of keeping the Alpine Light Down now is that I'm pretty confident in not hitting a bottom in terms of coldness with it + layers (at least in places that I would want to visit... -20 or higher). I'm thinking I can push the down inner + layers to 0, but I don't really know for sure. Will keep thinking about it for next few days before sending one back.
Hope this helps someone else. Let me know if you have any thoughts or questions!