Don't forget the "best" choice between down and synthetic for most uses outside of Alaska or the PNW - hydrophobic treated down! Repels water very well for anything short of a true submersion.
I've used a treated down quilt + SilNylon dry bag. In nearly every weather situation since 2015-ish and never had an issue with the down wetting out.
As important, if not more important, than your sleeping bag or quilt is your sleeping pad!
Check the R values on several.
Some companies have truer ratings than others (looking at you Klymit) and there is a push for an industry standard in the works. Phillip Werner over at SectionHiker.com has several great write ups on the subject a long with an accurate comparison table of the major brand offerings.
Other random thoughts on the subject:
Western Mountaineering, Feathered Friends, and Stone Glacier make some great buy-once, cry-once, lifetime quality down bags.
Nemo sleeping bags are notorious for being optimistic about temp ratings. Although they are very comfy for side sleepers like me.
Enlightened Equipment (verify actual temp rating!), Katabatic, hyke n' byke, and a great many cottage vendors make amazing quilts with warmth to weight ratios that are astonishing.
Look for a fill rating of 800 or above.
I've used a treated down quilt + SilNylon dry bag. In nearly every weather situation since 2015-ish and never had an issue with the down wetting out.
As important, if not more important, than your sleeping bag or quilt is your sleeping pad!
Check the R values on several.
Some companies have truer ratings than others (looking at you Klymit) and there is a push for an industry standard in the works. Phillip Werner over at SectionHiker.com has several great write ups on the subject a long with an accurate comparison table of the major brand offerings.
Other random thoughts on the subject:
Western Mountaineering, Feathered Friends, and Stone Glacier make some great buy-once, cry-once, lifetime quality down bags.
Nemo sleeping bags are notorious for being optimistic about temp ratings. Although they are very comfy for side sleepers like me.
Enlightened Equipment (verify actual temp rating!), Katabatic, hyke n' byke, and a great many cottage vendors make amazing quilts with warmth to weight ratios that are astonishing.
Look for a fill rating of 800 or above.