I would say it's 50% bulkier... You'll notice it in the bibs more than the jacket in my opinion. As for mobility I didn't have any issues shooting and I had to be in a goofy situation to make it. The only mobility issue is being able to raise your leg up high for tall steps on the tree.. but I think that's just a late season bib issue in general. Get layered up enough and it's going to be an issue. I always unzip the bib leg from the top down a ways walking in for venting, and that also helps a ton with mobility climbing into the tree. Once your in the tree and zip everything up it's a non issue.
When I would sit down with the Solitude and compress the insulation around the knee I could feel some coolness, which I could expect because I compressed the insulation. But I never ever had an issue with the Sanctuary set cutting wind and I had multiple days with 20+ mph winds when it was cold. I didn't wear the Solitude but a couple sits this year and for how I dress I like that system over the Sanctuary unless it's super cold. I like to have base layer bottoms on plus the Catalyst pant, then have the bibs over the top. Some like to just have a couple base layer bottoms on under their bib and in that case I'd stick with the Sanctuary. But if you like to have regular pants on underneath then I'd lean to the Solitude for temps 10-50. I'd say if you're only going to be using them 20 and under you'd probably want the Sanctuary.