I have both. They are for extreme cold and low activity. They work similar, the Wooltimate may be a shade warmer. It has been getting into the 20's this week with wind chills in the teens and I haven't broke them out for whitetail hunting yet while hunting every day. They suck to walk in and I have lighter, less bulky options I can put in the pack that I can put one once I get close to my hunting location.
I love my Wooltimate and Berber for when it's absolutely brutal cold and windy for riding a horse, ATV, or sitting. Anything short of that and they are to darn hot. Not much I've found warmer for the money though, I use mine a lot when we are calving cows in brutal cold.
The system below works for me in a lot of climates hunting, mixing and matching layers as the conditions demand. It is damn expensive though even buying everything on sale over time.
UPPER BODY
A First Lite Aerowool base layer
First Lite Sawtooth jacket
Sitka Jetstream Lite Vest
Kuiu Kenai puffy OR Sitka waterfowl puffy (1lb heavier and more insulated than the Kenai, less breathable)
Either a Krypek Dalibor II jacket or if it's really wet a First Lite Seak jacket for a top layer
I can be very active in some combination of the first 3 and warm when inactive with the last 2.
LOWER BODY
First lite Aerowool boxers
Kryptek merino base layer, Kuiu Pendleton zip off base layer, or nothing
Kuiu Kenai zip off base layer (when stopped and glassing for a while)
First lite Obsidian pants (or if stand hunting and leaning forward a lot Sitka Celcius bibs)
Kuiu Yukon pants (only if it's damn cold and also wet)
OTHER
Mild - Sitka Core gloves
Mid season - Sitka Traverse gloves
Cold Kuiu Glassing mittens or Aleyeskan wool gloves over Sitka Core gloves
First Lite merino baklava under hood
Darn tough full cushion boot socks
HPG mountain serape if it's real cold and I think the 40oz is worth it for the dead air space and warmth.
Probably more info than you wanted, but that's what I use hunting now. I retired the Berber and Wooltimate to keeping me warm on the horse or UTV when calving. Hunting I sweat to much moving and then froze when stopped with them.