I didn’t see any comments regarding fill weight. That honestly is a huge part to staying warm given a temp rating versus a certain brand. When comparing brands at the same temp rating always look at the size and fill weight. Western Mountaineering and Feathered Friends are known to be true to their temp rating D they use premium 850 - 900 down with conservative amounts of down.
also the REI marmot helium is listed at $430 right now and you can get a brand new Western Mountaineering Alpinlite 20 for $544. So for $114 more you ensure that you are sleeping the best you can in the backcountry.