Radiant 20 Sleeping Bag

I rarely see bags rated by the actual extreme survival rating. Bags that use that level of inflation rarely bother with the testing. Most bags seem to be rated somewhere near the Lower Limit Temp, which is kind of the comfort rating for warm sleepers. REI's product page seems to have this one rated between the Comfort Temp of 25 and the Lower Limit Temp of 13. 

In personal experience, I find quality down bags to be fairly accurate. The radiant looks like its comfort rating is 25 though and if you are near the rating it can be down to personal vatiations, how well you fit in the bag, and how well you sealed up the hood.  You can always add a warm hat and a layer of clothing like long underwear to stretch that rating a few degrees. 

I think your comment “I felt like there was some drafting coming in the face making my torso and arms a little cooler. Legs and feet were toasty.” May be a clue. The REI Radiant bag does come with a draft collar. Make sure it is positioned correctly and that the hood is tight around your face producing a good seal. You need to make sure you keep out the drafts. This may be why your upper body is cold while your lower body is warm. Otherwise a heavy sweater and hat might be all you need to compensate for the chill in your upper body. Good Luck and enjoy this season!

R value should be ok, but the bag is probably at its comfort limit for your sleeping then. Seems like you sleep cold, you can also focus on what else you wear while inside. How many grams of 600g? You can also try redistributing your down if your legs were warm maybe it’s all gone south leaving your torso uninsulated. 

I think your thought process is great. As a greenvest, my advice is always to use what you’ve got, then upgrade when you feel comfortable doing so. To your other concerns: Weight/packed size — Go to REI and ask to put them both in a compression sack. That’ll give you a good sense of that compressed volume and weight in the hand. Water resistance - Down and outer fabrics have come a long way since the old days, so they hold up to condensation and a little rain pretty well. You don’t want to dunk a down bag in a lake, but you also wouldn’t want to do that with a synthetic. It’d be a cold, uncomfortable night either way. Couple other thoughts: - The Radiant is comfort-rated to 25F, the Trailmade to 31F. So not only is the Radiant one pound lighter, it’s a fair bit warmer. - Down will last longer than synthetic — a lot longer if you take proper care of it. We’re talking decades. Synthetics tend to degrade over time, shed microplastics and lose their temp rating. They also get stinkier.

The detail on that bag's product page states that the ISO tested *comfort* temperature is 25 F. So, they've decided to call it a 20 degree bag based on something else than lab test results.

The bag seems to be ISO tested for a comfort rating of 25F. Since that's just 7 degrees away from the conditions you slept at, I wouldn't call it completely surprising, while it is true most people will feel comfy at the comfort temp. Things to do is make sure you're wearing either Merino wool or a technical base layer, then add something like a fleece jacket. A beanie, tube scarf, loose-fitting wool socks and wool gloves are also a part of a solid sleep setup.