The Marmot Hydrogen is the overall "best value" in our review, offering a superb balance of quality, low weight, packability, and performance versus cost. However, it's not the best price pointed bag. Instead, we chose the $160 Kelty Cosmic Down for that.
For $350, this contender is a stand out sleeping bag. It's comparable to many more expensive products, as it is lighter and more compressible than almost all of its competitors. While its low weight and compressibility were impressive, our review team also loved its well-designed hood. Also, several subtle features, like its short secondary zipper, helped make it a more versatile bag. The versatility allowed for better ventilation, thus making it easier to get in and out of. The Hydrogen was a contender for our Editors' Choice, though the Western Mountaineering MegaLite packed down a smidge smaller (it was also warmer and roomier for that same weight, but costs over $100 more).
If you're looking for a high-quality sleeping bag that's among the lightest and most packable (and uses 800+ fill-power down and a high-quality shell without completely breaking the bank) then the Hydrogen is tough to beat. It's worth mentioning that the 25F REI Co-op Igneo 17 is $50 less and is very comparable to the Hydrogen.