I just recently went through the same decision making process. What I determined was I don’t want a mid layer to have down or be wind proof. To me, a vest is a mid layer as much or more than it is an outer layer.
Down as a mid layer, even the hydrophobic treated down, tends to get lumpy/clumpy and lose loft when you’re exerting yourself when it’s under a wind/water proof shell regardless of whether you actually break out into a sweat.
And I don’t want it windproof because I found that having 2 windproof layers on means that I get virtually no breathability. If it’s chilly and I’m going to be exerting myself and a vest is warranted, that wind proofness turns out to actually be a liability for me. I get hot/sweaty with very little exertion and it’s just counter productive for me.
I also sleep in my vest and store all of my spare batteries and phone in my vest, so it has to have a chest pocket or ideally 2. This keeps my electronics from getting sapped by the cold and has worked really well for me in preserving the longevity of my batteries in the back country.
The vest I settled on was a Mountain Hardware Kor Strata. It’s a Primaloft Gold synthetic insulated vest and I paid less than $100 for it on sale. I used it on a 10 day trip in southern Colorado this past season. The weather was a little warm for early-mid October, but it performed flawlessly for the 11 day trip. And weighing in at just under 10 oz for a large, it was well worth its weight for my typical conditions. My only con against it would be having only one chest pocket. I prefer having two to store my batteries/phone at night, but the one chest and 2 hand pockets worked well enough as is, that I’m perfectly satisfied with it.
