I'm new here, first post actually. But I've owned about every hunting puffy available on the market. If you're looking for a comparison just between these two jackets, it's not even close. The Grumman is way lighter and way warmer than the FL 2.O. The fit is much better as well. The FL 2.O must be made for more round guys because the bottom of the jacket does not fit anywhere near snug to your waist causing unnecessary cold to get in. Cinching the jacket tighter does help but why should you have to do that? The cinching doesn't hold well either so you're constantly cinching it snug to keep cold out. The 2.0 just has a weird fit overall and that's surprising because it was supposed to be improved upon from the first version. The 2.0 also is just not very warm at all I have to layer quite a bit to keep warm during late season hunts. On the contrary, the Grumman I am warm in during 30-40 degree weather with just a t shift on underneath. It also fits amazing and snug to the waist. I'm 6'4'' 210 athletic build and went with the XL which is perfect. The brown/green color also just looks cool and you can wear it around town. Like I've said I've owned almost ever puffy out there from the Kuiu ones, First Lite, Sitka Kelvin Down Hoody, etc. and the best overall has to be the Grumman when you factor in weight, warmth, and color scheme so you can use as an everyday jacket. If you are looking for the warmest puffy on the market without factoring in weight it's the First Lite Chamberlin. It's a heavy, bulky piece but it's the warmest puffy I've ever put on but that shouldn't be surprising considering it's fill and weight. If you're going to be glassing in sub freezing temps for any long period of time, the Chamberlin is amazing. I love comparing full setups with other people so here is mine and I've gone through a ton of different options and companies over the years and here is what I'm currently settled on:
Uppers:
-First Lite Fuse long sleeve
-First Lite Klamath quarter zip in cipher
-SG Grumman Puffy brown/coyote
-Grundens Weather Watch rain shell in refraction camo (for only $89 this is an extremely durable and light and breathable rain shell you can hike in through brush/timber and it will hold up)
Bottoms:
-First Lite Fuse long john
-First Lite Obsidian in cipher camo (most versatile pant I've owned)
This set up has gotten me through 99% of hunts. The pieces I'm looking to add when the budget allows is buying the First Lite Chamberlin again for extreme cold and the grumman down pants. But a good base layer, a good puffy, and a good rain shell is all you need for most adventures. Hope this helps someone out there!