Sitka core middie. layers fantastic over your bases. Layers fantastic under your shell. Quit enough to hunt with if you take your shell off, sturdy enough for stand alone jacket, and it packs fairly small.
Late season glassing...Arcteryx Leaf Naga 1/2 zip fleece hoodie as a mid. Have a Sitka Core HW hoodie as well and it cannot hold a candle to the Naga for warmth, although sitka breathes better when moving. weight is almost identical. The Naga is the Patagonia R1 on steroids.
I wouldn't buy fleece because "if you could buy only one" makes me think money is an issue and a $20 Condor fleece or $40 eddie bauer fleece will do 90% of what a fanatic hoody will do for 1/4 the price. A pnuma heated vest will keep you FAR warmer than a fanatic hoody will for less money, and/or no outdoors company makes a quiet puffy like the celsius midi.
I went and looked and your from WI. If you’re not walking a ton to/from stand - you’re answer is Sitka Traverse Cold weather hoody. Will work as outer for sits into 40s and as an extra warm mid layer for well below freezing.
It’s camo so provides concealment. Has a built in face mask and hood that provides warmth and concealment. And for less than $200, it’s probably the best all around value that Sitka makes.