My .02 cents: both the Hawkes and Kirkland products are well made and exceptional buys for the price. Plus the lifetime Costco no-questions-asked full refund return guarantee on any brand from Costco.
Both do tend to run large in size. I bought a Large Hawkes vest and had to return it for a Medium (I'm 6'0, 185#, 42 chest 34 waist and the Large was just too loose. Medium fits great but still ample room for layering underneath. Both are fine with torso length, good coverage down to the tops of my rear Levi's jeans pockets.
Both brand jackets come with boxy torso's, good length waist and long arms. That's not a bug, for me (35 sleeve length) it's a desirable feature. Both have generous inside open-top kangaroo pockets for stashing gloves/phone/whatever. Outside handwarmer pockets are zippered.
Finish quality on the Hawkes is very good. Both my Hawkes vest and jacket (550 duck fill) do shed a little down periodically, but so do my Eddie Bauer Downlight vest & jacket,(800 goose fill) for >three + times the price. Seems hard to create a truly UL and packable shell fabric/liner that prevents down loss but still packs small/light, so I see it as a very minor tradeoff. YMMV.
Costco is even more QC-serious, if that's possible, with their signature Kirkland brand. Neither brand will let you down (pardon the pun). I use mine a lot for air travel, when flying from my warm location to someplace cold where I'm going to want warmth that packs flat & small in a carryon bag. Hiking ditto.
800 fill naturally beats 550, but Hawkes' 550 is pretty ample for most situations as an insulation layer. I've worn my Hawkes vest and/or jacket as a solo insulation layer under a thin unlined windbreaker/windshell and been perfectly comfortable down to 30'/upper 20's so far. I get cold easily so that's a real compliment to the Hawkes down.
Both are great buys. My Costco had the Hawke's vests priced down from $25 to $19 so at that price I grabbed a black, a blue and an olive drab. Costco only has these seasonally and does not usually restock so when they're gone they're gone even though Winter is just beginning for most of the USA. Don't procrastinate.
Costco also offers general around-town all purpose softshell winter jackets (Weatherproof is one brand I remember) that are fantastic buys at the price ($25-$39 range) so give those a look too. They also offer winter gloves with those fingers that let you use a touchscreen iPhone with the gloves on for insanely low prices.
Off topic but I notice Target near me has unusually good range of serious winter hunter's caps <$20, those synthetic fur/fleece jobs with the dropdown flap ears that make you look like a KGB Colonel (minus insignia). Not UL but insanely warm/windproof, great for serious winter & not always easy to find at dedicated outdoors chains.