Arc'teryx Atom LT vs Atom AR Hoody Review

Atom LT Hoody at Dawn
Many would consider the Atom LT hoody from Arc'teryx as one of the best mid-layers currently available. I've used mine countless times over the years and it's so popular that almost anyone that I pursue outdoor activities with owns one. The Atom line has gotten so popular that Arc'teryx has expanded it with the Atom AR and Atom SL. It only seems natural to me that some people may be confused as to which Atom would be best for them.

In reality, most outdoor gear reviews only focus in on 1 piece which is great in understanding how good or bad that 1 item is but most consumers, including myself, are comparing several items at once. I hope this review and comparison provides some valuable information that cannot be found elsewhere. I currently own the Atom LT and Atom AR, so the focus of this review will be comparing and contrasting the two and not the Atom SL (maybe a different review in the future).

Atom AR on the Coleman Deming Glacier of Mt. Baker

Outer Fabrics:
Both the Atom LT and AR use Arc'teryx's proprietary 100% nylon fabric called Tyono™. The linear mass density of the outer fabric of the  Atom LT is 20 denier compared to the Atom AR at 30 denier. This means that the  Atom AR has a slightly heavier but more durable outer fabric.

Synthetic insulation is measured different from down which is simply done by the weight of down in grams or ounces. Arc'teryx's proprietary Coreloft, is measured by the area mass density in grams / meter² (g/m²). Almost all synthetic insulation is made in large sheets of variable thickness depending on the warmth required. A thicker sheet of synthetic insulation will have a larger area mass density in g/m². The converse is true with a thinner sheet. Now that this is explained we can move on towards comparing the insulation differences between the Atom LT and AR.

The Atom LT uses 60 g/m² of Coreloft in the entire construction of the jacket with a hard fleece along the underarms that extend to the bottom of the jacket. By hard-fleece, I mean that the inside has a fleecy texture while the exterior is smooth like a softshell.

The Atom AR uses 120 g/m² of Coreloft in Main Body, 80g/m² under the arms, and 60g/m² in the hood. The Atom AR doesn't incorporate any fleece in the construction of the jacket.

The Atom AR has double the insulation in the main body compared to that of the  LT. Overall The Atom AR is quite a bit warmer than the LT but it does loose a little breathability because it lacks the highly breathable hard-fleece under the arms.

The Atom AR weighs just over 16 ounces compared to the Atom LT which weighs almost 13 ounces. One is looking no more than 3-4 ounce penalty in bringing the AR over the LT, not a lot of weight but it does provide quite a bit more warmth.

Atom AR on the Sulphide Glacier of Mt. Shuksan
How they Fit:
The Atom LT has a "Trim Fit" compared to the Atom AR's "Athletic Fit". What this means is that the Atom AR has a little more space between you and the jacket. Both jackets are cut extremely well but the Atom AR has more space for a heavy baselayer, softshell/hardshell, or another midlayer (fleece or thin synthetic/down jacket). If  you're using the AR with just a baselayer, you may want to adjust the hem drawstring to keep the jacket closer to you. The Atom LT doesn't have this issue as it's cut more aggressively. The women's Atom LT and AR mirrors the Men's fit in regards cut but with a standard feminine flair.

Women's Arc'teryx Atom LT hoody at Foggy Lake in the Mount Baker-Snoqualmie National Forest
I've taken the Atom LT hoody on more trips than I can recall, but this summer I've made a priority to use both the AR and LT to really get a good understanding of the differences between the jackets. I took the Atom LT Hoody to climb the South Spur of Mt. Hood and it was a wonderful piece for the majority of the climb as the weather was very warm. I only got cold when I was lowering my wife and brother off the summit into the old chutes while it was very windy on the summit.

Women's Arc'teryx Atom LT Hoody on the left and Men's Atom LT hoody underneath hardshell on the Summit of Mt. Hood
A little lower on the mountain, the wind was not a factor and the Atom LT provided plenty of warmth. I prefer the Atom AR for mountaineering or any camping that is done on the snow as it makes for a much better insulating layer to throw on at rest breaks or when the wind picks up. This was especially true for climbing Mt. Baker and Mt. Shuksan as I was happy I brought the Atom AR.
Atom LT Hoody just below the Hogsback on Mt. Hood,
The Atom LT shines best at backpacking, hiking, rock climbing, or as a midlayer under a shell for downhill skiing. On hiking or backpacking trips where rain is a possibility, I always bring my Atom LT Hoody as it provides excellent warmth even when wet or damp and doesn't weigh much more than a standard down jacket.

The temperatures in the PNW are generally pretty mild that I mostly use insulation pieces in static situations where I am stopping for a rest break or at camp. While it is true that the Atom LT is more breathable, I find both Atom jackets too warm to hike or climb in. This may not be the case if one is winter mountaineering or in really cold places.

The Atom LT and AR are both outstanding jackets. I believe the Atom LT is best suited for the person who is looking for a synthetic insulated jacket for non-snow related activities where the temperatures are pretty mild and breathability and weight are more of a factor. If you only want one synthetic jacket that extends the use to include mountaineering and snow camping or you simply run a little cold, then I think the Atom AR provides more versatility as it provides more warmth and layering options without much additional weight or cost.

Pros and Cons:
  • Atom LT is 40$ cheaper than AR
  • Atom LT is 3-4 ounces lighter than AR
  • Atom LT is more breathable than AR

  • Atom AR is a lot warmer than LT
  • Atom AR is slightly more durable than LT
  • Atom AR has more layering options than LT
Men's Arc'teryx Atom LT hoody at Foggy Lake in the Mount Baker-Snoqualmie National Forest


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