Imo, the best way to get a feel for how brands hold up is to wander around a thrift store, even if you don't want to buy anything, and check out tags. My Goodwills are full of 'mall brands' so it's easy to see what's held up and what hasn't (and a lot of those stores even mark what season & year the clothing was sold in). To be honest, it seems to come down more to material/fabric/etc. than brand: I've got cotton blouses from Old Navy through Banana Republic/Ann Taylor that are still looking beautiful, but when I see knit tops (glorified tees) from the same brands they're usually showing their age more. That said, the cotton is usually softer/silkier in the higher end brands. My silk blouses seem to hold up equally well regardless of brand (I wash them all on the hand wash setting of a front loading machine, then hang to dry). My favourite summer fabric is probably cotton/silk blends, often form the Gap or Banana Republic: it has the most wonderful feel to it.
Oh and my tees that I've thrifted second hand, and thus been happy with the quality of them surviving whatever their first lives were, are J Crew, Banana Republic, Gap, and Old Navy; they've all held up well but I don't wear tees that often. They're all 100% cotton; my favourite random brand cotton knits (tees and leggings) are organic cotton.
Almost all of my non-vintage wool cardigans are from J Crew, but they're not all the same quality: most of them have the ribbon backing along the button band and are holding up beautifully (I wash the same way I do silk tops, but dry them flat) but a couple don't have the ribbon backing (newer perhaps?) and while they're still holding up/not pilling I do miss it/notice the difference. I have a wool/acrylic blend form NYC Company that isn't as good quality. Most of my newer (aka not vintage) wool/wool blend pullovers are from Gap/Banana Republic and I've noticed most of them need a good de-pilling session, but hopefully after I've done that they'll be good again. My cotton/silk/linen cardigans are all holding up quite well; in fact the linen/cotton blend from Old Navy is one of my favourites. The one that's ageing the fastest is probably a 100% cotton Merona one, which is a Target brand.
I have a couple pieces from Talbots that I really like, and the stuff I came across from that brand while thrifting often is made out of delicious fabric. I wish I found it more often in my size! Ditto to Eileen Fisher.
As far as trousers go (by this I mean non jeans style cuts), I was surprised to discover that the ones that tend to fit best/bag least/hold up well have a bit of man made fiber in the mix. I usually prefer natural fibers, but checking the tags, my favourites tend to have a bit of rayon or nylon or polyester added to the cotton. The brands are Gap, Banana Republic, Ann Taylor, and some random brand my sister got for me at Marshall's; I haven't noticed a quality difference. My winter wool trousers have held up well but they're both vintage. I have a pair of tropical wool black trousers by Piazza Sempioni (Audrey cut) that are very nice quality, but I don't wear black unless the occasion requires it, so they're not subject to much wear. I would *love* if they magically turned grey overnight, because tropical wool is one of my favourite fabrics but very difficult to find while thrifting, at least here in south Texas.
I have a few pieces by different Anthropologie brands, but I'm not sure how old they are. My cotton velvet blazer by elevenses is beautiful: it's completely lined in silk and a piece of art. My cotton & silk blouses are by Fei and Odille (might be another one, I'm doing this from memory) and I love them, although I did have to repair a split shoulder seam on one of the silk ones. I have a skirt by Fei that is full of the loveliest details, on the inside where no one knows about them but the wearer, which is a sign of quality to me. But when I thrifted it it still had its tags on so I can't speak much to durability yet!
Wow, I've written a novel. Sorry about that, but I hope it's a bit helpful! There are various things you can check before buying that will give you hints about quality; often the same brand uses multiple factories, and different brands might use the same factory, so things can vary. An internet search or two should bring up information on what to look for!
P.S.: the wool coat I've had the longest & worn the most & is still going strong is from the Gap, 80% wool, 20% nylon. Since Gap is often considered 'fast fashion,' that might be a surprise, but there you go!
