I can't help with comparison, as I've never used either. But, I did order the Patagonia Ultralight Down Jacket last week (hooded). Then, earlier today, read a "State of the Market" article here, on ultralight down jackets.
I'm not even a noob backpacker yet - I'm in the planning and gear aquisition phase of becoming a noob. Now I kind of wish I'd read that article earlier...
After reading the article, I think I may well have chosen the Montbell for my purposes, had I read it before ordering. The Patagonia with multiple zippered pockets etc, I "suspect" won't do as well as the Montbell in a warmth for weight comparison. I don't know that for a fact though, can't remember the specs of the Montbell off the top of my head.
Since you mention far more multiple use scenarios, including urban, your choice may well head towards the Patagonia anyway though.
One other thing I can mention that might be of some use, is to shop around for a bit if you choose the Patagonia. I found it for just over half of what REI charges. The place I ordered it just last week (6pm.com) doesn't have them now, but from the research I've been doing the last couple of weeks, I think with just a little bit of looking and patience you can find it for around $170. Save your REI dividend and discount for other gear perhaps?
Lastly, and I just want to get this out there since this is my first post on the forum - I think access to the information here that comes with a membership is WELL, WELL worth the price for an aspiring noob like myself. I'm going to save the membership cost many times over in making more informed, practical purchasing decisions because of the information here. The article I mention above, has precisely the information you need to make an informed choice in this specific instance.