"Dan, I don't understand why, but I find that my UL Down Inner Parka has a bit different fit than my Alpine Light Parka. I am 5'10" and 200 lbs. My ULDIP is a size XL and fits me wonderfully. When I ordered the Alpine Light parka, I assumed I would also need an XL in it too, however, after it got here, I figured I could have went with a large and been just fine... but, I didn't feel like going through the hassle of sending it back and swapping it so I just kept it... I still kind of wish I would have just swapped it to begin with, but oh well. Anyway, more recently when I picked up an Ex Light, I also ordered it in an XL, and it fits me great to, just the same as the ULDIP."
The reason that the EX Light and the UL Down Inner fit you tighter in XL in comparison to the Alpine Light, is because the EX Light and UL Inner are intended to be used as a mid-layer to fit under a shell. The Alpine Light is intended to be to be more of an outer layer, which you can fit layers underneath.