marmot hydrogen or mont bell ul ss #3

I have a MB SS UL Hugger in a lighter weight, and it is a very nice bag.
They have a good design with that "stretch" design, because it stays close around you and keeps the insulation close to your body for best results. It warms up quickly, because there are no large open areas inside the bag for your body to have to warm up.
But they do feel a bit snug, especially if you are a stocky build.

I have no experience with Marmot bags, but they do have a good reputation.

My other bag is a Western Mountaineering Alpinlite, and it is an awesome bag, but very expensive.

Well cool cause i was gonna post that I love Marmot bags but since I've never used a MontBell I backed out, only to see someone had done the opposite.

Marmot SBs and MontBell anything are top notch. Which color do you prefer? ;)

Marmot bags are great. And, if you're not in a hurry, there's the plasma 30 — I bet a few will be popping up here soon on gearswap.

The Montbells used to be horribly underfilled. However since the use of EN testing, the bags seem to have sufficient down for their rating. I have had both.

If you like additional room to move and layer in clothing, the Montbell is the far superior bag. I also found the Marmot to have horrible DWR, whereas the MB was much better at shrugging off dew.

I agree with all of the above comments. I have the MB SS #3, which I purchased last year. It seems to be accurately rated, and has awesome DWR! I read that the heavier Hydrogen is a bit warmer, so it might be the better choice if you're likely to be pushing the bag's lower limits rather than exposing it to dew or dripping condensation.

I like the stretch of the MB, especially since this bag often sees temps way above 30F. I often use it as a quilt when it's above 50F or so, and when zipped up, I can stretch it open to vent excess heat if I wake up hot.

My winter bag is a 0F Marmot.