Arc’teryx Proton LT vs Atom LT: Main Differences [Guide 2023]

I thought it would be better, if I start comparison of Arc’teryx Proton LT vs Atom LT, because they are very similar. The main difference between Proton LT and Atom LT is the amount of insulation being used.  The Proton LT contains 80 g/m2 Coreloft Compact of insulation. On the other hand, the Atom LT uses 60 g/m2 Coreloft Compact for the insulation. This makes huge difference between those two and changes their warmth, compressibility, weather resistance and comfort performance.

Here is the list of key difference between Arc’teryx Proton LT and Atom LT and side by side comparison:

I had an Atom LT previously and thought that its performance while ice climbing was great with a merino base layer.   The only thing that I didn’t like was the bulkier fit and the panels on the side which sometimes made me cold which is the expense of breathability.  This Proton LT solves all those problems. 

Warmth & Insulation

The difference in insulation is quite significant between the Proton FL and the Proton LT. The choice will come down on your priorities. If you need a jacket mostly for belaying and colder days, the Proton LT will be your best choice. If most days are fairly warm but you still need a lightly insulated piece for overall comfort, the Proton FL might be the best choice.

The Proton LT is warmer than the Atom LT. You will see, It is also more thermally efficient and durable/abrasion resistant, thus it is more versatile. The key point that makes their warmth level to alter is the amount of insulation being used in their built. The Proton LT uses Coreloft Compact 80 gr/m2 of insulation. However, Atom LT uses 60 gr/m2 Coreloft Compact.

Versatility & Breathability

The Proton LT is a versatile mid-layer and a standalone piece that has been designed for high output activities (considering breathability). It is highly air permeable piece that will provide warmth during activities where breathability is the priority! The following chart is from Arc’teryx Own website, they claim the purpose of use for both Arc’teryx Proton and Atom.

Atom LT’s face fabric Tyono™ 20 offers decent breathability, but it still lags behind Proton LT’s Fortius™ Air 20 which is air permeable.

Durability & Wind Resistance

Face fabric itself of the Atom jackets is more wind resistant than the Proton LT, because the breathability is a key design factor on Proton LT. If you are wearing both jackets, you will notice that the wind penetrates the core and the arms much more with the Proton compared to the Atom.

From the durability stand point, the Proton excels the Atom. The face fabric of Proton is abrasion resistant.

Fit Arc’Teryx Proton vs ATOM

Both jackets do fit differently. The Proton is more fitted, but it’s longer and has more room through the shoulders.  I have to size up in the Atom LT. However, don’t need to in the Proton LT due to its shape.

In general, fit of the Protons is narrower than the large size in the Atom line up.  Especially through the torso which is better for layering.

Bottom-line for Arc’teryx Proton LT vs Atom LT:

For comparison, the Proton LT is a highly air-permeable version of the Atom LT. The Proton fits better, if you are planning a high output activity. Honestly, I prefer my Arc’teryx Proton over Atom. People like me who experienced both product usually says “I started with the Atom line up but the Proton is where I should have started.”

If you are looking for a mid-layer that is both breathable and durable while still providing warmth the Proton LT would be my recommendation.

If you are looking a mid-layer Under Arc’teryx Alpha SV, the Proton LT will be better than the Atom LT at heat dissipation.

You may consider checking the following good review for Atom LT:

The Proton LT: