Howdy,
I did the Crawling Road videos on the Akto and Soulo. I own and have used both. I'll make a few comments.
The Akto is my favorite solo tent. It is easy to setup and lightweight for the protection it offers. I have been in many storms with it and it has always kept me warm and dry. However if I thought for SURE I'd be getting lots of snow I'd probably want a Soulo due to the pole construction. The Akto works fine in lighter snow, but out where I am we get heavy wet snow and the ends tend to want to bow in a little. You can knock the snow off and it's no big deal. But if I was thinking of being in a serious snow storm with it I'd want to keep an eye on it.
The Soulo is a very strong tent. Way stronger than just about any solo shelter I've seen. However you pay a weight penalty for this. If you are winter camping using a pulk you may not care about the 1.5lbs. more weight though vs the Akto. But I carry it in my pack and I feel comfortable having it if I'm thinking there is going to be serious snow. Sometimes 1.5lbs is worth it for peace of mind.
The Soulo has a vestibule for stowing gear. The Unna does not. I live in a really wet part of the US so I like having my gear outside under a vestibule and not inside with me. The Unna you could detach part to get a pseudo-vestibule, but this is kind of a hack.
I don't think I would cook necessarily in any vestibule on the solo tents, but you could use a propane stove in them if you must. I wouldn't use liquid fuel in any tent.
Also have you considered the Nallo? I am going to try one, but they are also a storm worthy tent with reasonable weight and a really big vestibule.
Re: Weight of Hillebergs
I was very fortunate this Summer to go hiking through Sweden and Norway. I actually got to spend a day with Bo and Renate Hilleberg for lunch as I was in their neck of the woods. They toured me around their design offices and it was like getting a PhD in tent design. They have very specific reasons for the fabrics they choose for their tents and take it very seriously. They are obviously aware that there are lighter fabrics out there, but they continue to use the Kerlon series because it is stronger and has much better storm survivability in their tests.
Not just this, but fabrics are all subject to UV light degradation immediately. By using a stronger fabric Hilleberg can ensure the tent will last for many years of tough use vs. other fabrics which are just thick enough to work well during a review (and grab lightest tent award), but will tear like tissue paper after a season of use and exposure to the Sun. Same reason why they use thicker zippers, etc. Those parts break down in the field and they want to be sure they are reliable.
They are very serious about storm worthiness because their tents are used in such bad environments. One reviewer wouldn't rate their tarps because they said they were "too heavy". But the Hillebergs refused to use a lighter material because they felt it would compromise the safety of the user in a storm. They even have a custom made snow blowing machine at their facility where they can simulate 70+ MPH winds with rain/snow. They will make their designers stand in the wind and setup the tent to be sure it can go up quickly and safely, not to mention survive in bad conditions.
So yeah they are heavier somewhat. But consider that the tent will last you years vs. other brands I've seen and won't get ripped to shred in a storm and it's easy to see why the weight is worth it. There are no free lunches and having a shelter fail in bad weather will have most people begging to carry one extra lb. to have a better tent.