Arcteryx Atom LT or Montbell Thermowrap jacket

Hey Zach,

Hope all is well.

I have no experience with MB Synthetics, but have used a lot of their down
kit and it's top notch.

I had an LT for a while but changed it out for a Nuclei which I absolutely love.

The Nuclei is far warmer than the LT and a lot lighter

I wouldn't bother with the Atom LT. It is a great jacket but the fleece sides make it a poorer, less efficient choice for backpacking. I would consider the Nuclei instead, which compares favorably to the Thermawrap Pro.

Just wanted to chime in on my experiences. I went into hypothermia in AK three years ago wearing a Patagonia merino 1 shirt, a R1 full zip jacket, a Montbell U.L. thermawrap and an Arcteryx rain jacket. I was on a remote beach in the Kenai, temps in the 38-42 F range, wet with wind. I have since gone to a Patagonia Piton hybrid hoody, Ghost Whisperer, Nuclei, Cap 4, nano air and MB Mirage as my options. In my many experiences I found the R1 and U.L. thermawrap not very warm. I hope that helps a little.

After getting sick of babying down in the wet I just bought an Atom LT. Chief rationale for me was fashion as I wanted something I could also wear around town. It delivers 100% on the looks front, even leaves my Patagucci ultralight down hoody for dead… so I suspect that is what you're paying for and this may or may not matter to you. Face fabric is also pretty nice, which may contribute to cost.

In terms of true function, the hood is really nice (big enough for my huge head, unlike Pata down), and zips and cuffs are also good. Warmth doesn't appear overly compromised by the fleece panels, and the ability to let warm underarms breath is quite nice… all in all I think it's pretty well as warm as a nano puff pullover I have, maybe even a little warmer due to a trimmer cut (although nano puff is a couple of years old so take that with a grain of salt). No idea how this compares to MB.

del

That may be true if you actually want an exclusively active garment, but my understanding is that alpha blocks very little wind, so for backpacking insulation which is often passive it will be generally poor… The LT is at least mostly windproof, but can dump heat more effectively if you do want to wear it moving… then if the is wind really up while sitting around at camp you can happily throw a windshirt over or under and then all that is really lost is the difference between fleece and 60g coreloft on an area that doesn't need a tonne of insulation (for example the R2 also only uses light fleece instead of high loft in this area).

Granted, alpha + a windshirt may work just as well… but that didn't make much sense for an around town use case, which is obviously where the dead birds excel over other brands :)

but that didn't make much sense for an around town use case, which is obviously where the dead birds excel over other brands

the plan truth !!!

;)

I can't comment on the MB, but I have an Atom LT (LEAF Version, so it has more durable fabric, a hood fastener, a different hem, and 'cord routing' ports through the pockets) that may be one of the best pieces of gear that I own.

No, it isnt that warm. But with layers, I have used it well below freezing. It is not as warm as a nano puff- but more warm than the Nano Air. The fit is top notch.

It's a great, versatile piece with a WIDE temperature range. But standalone, a lightweight down puffy would be much warmer.

I've tried both of these jackets out breifly before settling on an Arc teryx Nuclei. If you're long and lanky like me, the Atom LT is going to fit better. I returned the MB Thermowrap I bought a couple years ago because the fit was just too boxy and too short for me. In contrast, Arc teryx XL fits my 6' 5", 225lb frame exceptionally well.

That being said, the warmth is probably pretty close, depending upon how you use them: 50g insulation w/ no hood (Thermowrap) vs. 60g insulation + the stretchy side panels on the LT. Have you considered the MB Thermowrap Pro or Thermowrap Sport? The Pro has 80g insulation and a hood, while the Sport has the stretchy side panels like the Atom LT.

Personally, I'm really happy with my Nuclei for non-to-moderately active pursuits in cold, windy conditions. Perfect fit, super light and very comfy.
Good luck in your quest!

It depends on what you want to do. I have the Thermawrap and the Nuclei and returned the Atom and Mountain Hardwear Thermostatic after trying them on. The Thermawrap isn't as warm but good for cool not cold temps and cheaper. The Atom is probably best for wearing while active in cold temps but I was concerned about wearing it in camp on cold nights due to the fleece sides. For sitting around camp or adding temp range to your sleeping bag, the Nuclei is probably best. If the trim fit is an issue, the Mountain Hardwear Thermostatic is lighter and seemed just as warm but it was a little boxy on me.