Long answer:
Are you asking what the equivalent to 60g Coreloft is in a down fill value? If so, you’re asking the wrong question- that’s like comparing height and weight. Ounce for ounce, a high end synthetic is about as warm as 550 fill down. It’s hard to use this to compare most synthetic jackets with down jackets- they tell you the weight of Coreloft in grams per square meter vs the total weight of down and the fill. There’s no way to directly compare these two numbers- you’d need to know the total weight of insulation in the Atom LT, or the weight of the down in grams per square meter given the loft thickness of the baffles in the Down Sweater.

Since Coreloft is a proprietary insulation with no technical data available, I’m going to assume it’s just as warm as PrimaLoft One at the same weight. It may be a rebranded PL1. If it isn’t, it’s likely not quite as warm as PL1, but close enough for comparison’s sake.

Patagonia Down Sweater = Iclo 2.14
Patagonia Nano Puff (60g PL1)= Iclo 1.51
Atom SV & Patagonia Micro Puff (100g PL1) ~ Iclo 2.40

I’m not sure how to factor in the Power Stretch panels on the Atom LT, which don’t insulate as much- intentionally. With the Power Stretch panels, I’d guess that the Atom LT hoody is around half as warm as the Patagonia Down Sweater Hoody. This matches my experience with my Atom LT Hoody and down jackets similar to the Patagonia.

All of that said, these are garments for different purposes. I don’t ski, but I do hike, snowshoe and kicksled. I love the Atom LT for cold weather exertion, ~20 deg F and below. Atom LT with a shell on top is almost as warm as something like the Patagonia Nano Puff with a shell. When I get going, drop the shell and allow the side panels to vent. If I was wearing the Nano Puff, I’d be way too warm and would have to shed the Nano Puff entirely.

If I wanted camp insulation or a daily jacket, I’d get the Patagonia Down Sweater Hoody. Down will last a lot longer than the synthetic insulation, too.

Hope that wasn’t too long!