Anvil Horn 45 Degree

I have quilts for summer to fall temps, and for into the 20s. Below that I have a 0F bag. No zipper to fight with is enough of a plus to me to choose quilt over bag. For backpacking they're a no brainer. Lighter, more compact. I roll in my sleep and the draft issue isn't true if you buy the right size. Must have a top shelf pad. For car camping, I'd want one of those top entry, no zipper, beds like the new one from north face. But I don't care camp. But, full disclosure, I switched to a hybrid for all conditions. Big Agnes Anvil Horn 45F. It's like a quilt in that it only has insulation on top. The bottom is just a sheet of fabric that also acts like a fitted sheet over your pad. I just add in a fleece liner for cold temps. The bag has tie loops inside to integrate a liner. The pad arrangement eliminates any tangling from rolling in your sleep with a regular bag (don't have that with a pad). The stability of the system is what I love. I love it.

The older I get the thicker the sleeping pad... Where I live, I need 3 distinct sleeping bags - warm weather (Big Agnes), shoulder seasons/early winter (Nemo), and extreme winter (Big Agnes - takes up the whole backpack!) I have an REI half dome tent - big enough for weekend camping, small enough that I could backpack with it if I'm not using a hammock. I also have several Coleman Sun Domes as lenders, and my boys each have a Kelty when they don't hammock. For front country camping, a nice comfy camp chair is worth its weight... consider a lightweight backpacking chair as an addition or alternative. You can enjoy a lightweight camping chair in camp, but hard to take an XXL rocking camp chair backpacking... Consider hammocking, too, but that's a whole additional rabbit hole to travel down.

Since it's currently at full price, the Magma is about $100 more expensive than either of OP's choices. The big difference is that has 800 fill power down, where the other two are 600 and 650 fill power. My daughter recently replaced a synthetic bag she bought while in college with an REI model, and liked their new sizing system. I think she may have bought the REI Magma. I have and like a Big Agnes 650 down bag I've had for years, but at a 15 degrees F rating, it hasn't gotten a lot of use in recent years. I agree with u/TheBimpo that, unless they are trying to put a full set of gear into a pack of 50 liters or less, OP will do fine with either of their choices.

I have a Big Agnes single I LOVE so I’m jealous of all the folks here with the double. We have a flatlands fleece double bag and the Klymit double pad because they were the easy buttons through our wedding registry. The bag packs large for my taste but the pad is perfect. We sleep on top of each other at home and love snuggling all the same in the wild. Unless your trips are all ultralight backpacking, it’s quite cozy and romantic!

I would go with a quilt, they are great for moving around. Zenbivy is most peoples favorite, I really enjoy my Big Agnes.