In reply to tt:
There are a few arguments as to why soft shells are cut close:
For climbing (esp. ice climbing), excess material can get in the way. They rely on stretch fabrics and appropriate ease in the cut (e.g. underarms) to provide the necessary mobility.
There's an argument that a close-fitting shell can shift moisture through the fabric before it cools and condenses, rather than cooling in the dead air space of a looser-fitting garment.
You might a bit of room to fit a thicker base layer, or thin mid-layer under it.
For soft shells that purport to offer mositure management via wicking, a closer cut makes this wicking more efficient.
Some jackets have very close-fitting sleeves, which cannot be pulled up for cooling; I prefer a looser fit for this reason, with a cuff fastening.
And, frankly, there's a bit of a 'new aesthetic' thing going on with close-fitting soft shells, especially Arc'teryx, who seem to design them for wedge-shaped superheroes.
There was a very good article about softshell on MEC's website (rennies_softshell.pdf), but they seem to have taken it down. Which is a shame, as it discussed the closer fit:
"The new silhouette. Soft shell garments have a whole new look – typically
slimmer, shorter, more body conscious and athletic (than the hard shell jackets they
will typically replace). Waterproof/breathable hard shells have been around now for
more than 20 years and it’s getting tougher for designers to create a unique new hard
shell look. As hard shell is getting tired, soft shell offers a refreshing alternative and
it’s this new “look” that ultimately will drive the market."
I think it really comes down to personal preference on how close-fitting you like your clothes to be...
