My frame of reference comes from a Arcteryx Leaf Naga hoody (a relative of the Delta but in stealth green), Kuiu Peloton 97 1/4 zip, and a Macpac Nitro.
The Arcteryx is too heavy for its warmth, so is only used ‘around town’ or front country. Although its the best all around piece, it just isnt light enough at ~12oz (Full zip, size L, with hood)
The Kuiu is great and the most versatile and ‘normal looking’ of the high performance fleeces. It breathes well, dries fast, and is warm for its weight. I use it as a cold weather sleeping layer, as its the same weight as a merino 120 T shirt but warmer. Its normal enough you can wear it into town and not look weird.
The Macpac nitro is the warmest of the bunch. If I wear it as a base layer and put my Merino 120 long sleeve over it (to block wind/trap warmth) this combo is good for summertime temps down to the 50’s. The alpha 90 fleece is significantly warmer that the Peloton at the same weight, but that is only true if there is zero wind (as in not even a walking speed wind) or you have an outer layer to break the wind.
My buddy just got the new Patagonia AirShed Fleece? or whatever their new one is that replaced the R series. He loves it. Its 6oz in XL and a 50/50 merino/poly blend, which is a great combo of warns IME. I cant comment on warmth. It looks ‘almost normal’ as its a continuous weave, but has a wavy texture to it
If you’re out for absolute warmth-to-weight, Stephen’s article shows that a dual layer alpha 60 fleece had the highest W:W of any fleece. That would need to be custom ordered from timmer, farpointe, vado, etc.
If I could only have 1 UL fleece overall, it would be the Kuiu because it hits a sweet spot of warm, comfortable, light, and borderline normal looking. Also it does not snag on EVERYTHING like alpha direct since its a continous woven fabric (God help you if Alpha and Velcro hooks meet)
If I was trying not to bring a Puffy and only bring a fleece for summer temps, I would choose an Alpha Direct product like the Macpac Nitro or other 90gsm or 2x60gsm. Anthough it requires being more careful, looking nerdy, and requiring a wind breaking layer to retain any warmth at all, it excels at breathability and W:W, thus fueling the hype train.
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