Botha re good, here is the short rundown on the differencesBoth are good choices, I don't think there is an iMirage this year, Westcomb went to just Mirage. Shuksan is slightly longer than Mirage and has a squarer cut (for the lack of better description). Mirage has a fancier cut, but it is does not look as slick as Arcteryx's coats. I tried both and ended up liking the Mirage more for only one particular reason-Shuksan is a collarless jacket and Mirage has a collar. Also Mirage has the collar stiffener in the back that Shuksan does not have. As the result the hood pulls the front part of the Shuksan towards your face (hard to describe in words, but you end up brushing your chin against the zipper; this is also the reason Arctryx puts collar stiffener in their jackets: they push the zipper away from your face). In all other aspects I liked the Shuksan more: good zippers, more pockets, larger pockets, and usable inner pockets. At $289 or so list price it is also a good deal for a top-end coat. I am going to return my brand new orange Shuksan to REI, so someone could be happy and sweat-free this season.
P.S. Obviously Mirage is made in Canada and Shuksan in China, but I don't really see any glaring quality differences. Looks like REI got a huge hit on their hands this season. Shuksan pants also look top-notch, this is probably what I am going to end up skiing in this season.