On a couple of winter hikes in the last few days (once in the teens, once in the low 20s), I've had a chance to try out two new Power Dry High Efficiency hoodies — a Patagonia Capilene 4 Hoody and a Marmot Thermo Hoody.
Patagonia Capilene 4 Hoody

Marmot Thermo Hoody

On both hikes, I wore these as the only layer over a light long-sleeve synthetic baselayer shirt while I was moving. Both were high output hikes with significant elevation gain and the potential to sweat profusely. These two, nearly identical hoodies, were fantastic. Keeping me just warm enough but breathing enough that I stayed dry. In both cases, there were also the only covering on my head — although I started out with beanies for the first mile each day and took them off.
FABRIC:
These use the same Power Dry High Efficiency fabric. It's a very light gridded fleece with a loosely woven exterior. Same rectangular grid size. Same pile thickness. Same size channels between the pile. Just one difference. It appears that Polartec uses a more aggressive final brushing on the Patagonia fabric, so the edges of the rectangular grids are a bit more ragged and abraded away. The grids on the Marmot are more cleanly rectangular. I don't think it makes a bit of difference.
Patagonia fabric

Marmot fabric

STYLE:
Functionally, these two hoodies are nearly identical, differing only slightly. The Patagonia is styled more like a base layer shirt, with a half-zip, shirt-style hem and shirt style cuffs. The Marmot is styled more like a jacket, with a full zip and elastic binding around the hem and the cuffs.
DETAILS:
Both have a zipper chest pocket. The Marmot has conventional thumb loops and longer cuffs, like a running shirt. The cuffs are tight enough to stay down under glove and I could only push them up short of the elbow. The Patagonia has conventional shirt cuffs with fabric thumb loops. In comparison, they don't stay down under gloves quite as well, but they can be pushed up easier/farther.
HOODS:
The Patagonia has more of a balaclava hood with a small opening. It can be easily positioned over the mouth and even up over the nose. The Marmot opening is larger. It can cover the chin, but not comfortably over the mouth and nose. The Patagonia hoody is a double layer of fabric so it's warmer. Marmot hood is single layer fabric so it breathes better. I guess which one would be preferable would depend on how cold it is. Since you could wear them with a beanie or balaclava, I guess the thinner hood would cover a wider range of temps. But, both hoods are fantastic.
SIZING:
At least in Men's Medium, the cut and sizing seems to be pretty much identical. Both are tight fitting "athletic" cuts designed to be snug over bare skin or, at most, a thin baselayer.
WEIGHT:
Essentially identical. The Patagonia weighs 227 grams, 8.0 ounces. The full zip Marmot weighs 230 grams, 8.1 ounces.
In summary, these are awesome pieces for cold weather activities. I see them as a perfect "step down" from a Power Stretch hoody, when the activity level is generating too much heat for a thin Power Stretch. These things breath like crazy — they offer virtually no wind or rain protection. They were just about ideal for cold weather hiking.

