Bumping this back up while I mull (or agonize) over details. So here's a case study in details:
I'm in the market for some breezy long sleeve tops and pants, things that are light enough to wear well into summer and still provide full sun protection. I've got options carted at both Uniqlo and J Crew, and will probably just end up placing parallel orders and cross my fingers that *something* fits. I'm really hoping that the J Crew items work, because the details are more appealing to me, but I know from past experience that I have better luck with the cuts and sizing at Uniqlo. I just don't find the Uniqlo versions to be nearly as exciting as the J Crew options, and here's why:
Saturation -- I really like my colors to be pretty saturated. Deep, rich, vibrant. Even though both of the pants below are dusty green, I think the J Crew green is much more appealing, has a little more oomph. (However, I'm often pleasantly surprised by Uniqlo colors in person vs in photos, so we shall see.) And of course, that gingham shirt is just eye-poppingly awesome. I like it, although my rational brain knows that I would also make good use of the solid blush top from Uniqlo -- it would be a direct replacement for a similar pink linen shirt I got rid of last year.
Pockets -- I like that the J Crew top has one. It gives it a bit of asymmetry, and a bit more of a menswear vibe, which always appeals to me. I like the tomboyish vibe of the patch pockets on the J Crew pants. And I often find slash pockets, like the ones on the Uniqlo pants, to be unflattering, especially in lighter weight fabrics where they can disrupt how the pants fall.
(No) Drawstrings -- I am pretty much always anti-drawstring, on both pants and jackets. I find them fussy, and I don't find the cinched waist look to be particularly flattering on me. On the Uniqlo pants, I worry that the drawstring might be pushing these too close to pajama territory for me (I know, I know, it's a trend, but it's not my cuppa).
Stitching, piping, and other contrasting elements -- I love any element that brings a little pop or contrast. Piped pants and jackets, contrast stitching, jackets with bright fun linings, selvedge denim, etc. I will admit that one of my greatest weaknesses is the signature red stitching on Uniqlo's IDLF line. I'm such a sucker.
So anyway, those are some of my make-or-break details. However, for me, I think they are not truly make-or-break. The real bottom line is always fabrication and fit. I can love the design elements, but if the garment feels cheaply made, or made for someone else's body, I'd rather just let it go than end up in a love-hate relationship.