I'm a self admitted jacket junkie.
In my extensive jacket collection I own the following shells:
Arcteryx Alpha SV
Mountain Hardwear Berrylium
Patagonia Stretch Element
North Face Modulous
Out of all of these, the Modulous (yes I know it's not the Mammatus, but it's the previous model) is by far the weakest. It's too overbuilt, too much bulk and the one I don't even take off the rack anymore. It's not horrible quality or anything, it's just when comparing the high end models of these 4 companies, it comes up lacking quite a bit in comparison.
The Stretch Element is a beast, as is the Alpha SV. Sometimes its hard to pick between them, although in the location where I live, in the realy nasty weather, I go for the SV, it's longer, got a better hood in my opinion, as well as a waist and hem cinch as opposed to only the hem on the Stretch.
The Berrilyum has been a suitible workhorse as well, quite a nice changeup and I have no negatives to say of this one overall, except the hood is harder to adjust and is more of a pain.
If I had to choose only one, the Patagonia or the Arcteryx would be my choices, although I have been curious about the mammutus, but the modulous has left a sour taste in my mouth.