Bell tent/Yurt vs Southern Cross Ultimate?

I can't help you about tents but please be aware of the risk of carbon monoxide poisoning if using a gas heater in an enclosed space like a tent.

Judy and I now use a Southern Cross canvas tent. I am not sure that it was called an ultimate back then, but it is still a rectangular tent of the same size , using the side pole kit, and deleting the centre pole. Ours is about 20 years old now, and we have only in the past 4 years started to use it more and more after removing our roof top tent. If buying a new canvas tent, make sure you set it up and let it get wet as for the stitching holes to seal, or if does not look like rain use a hose and soak it down.
As we are in our late 60's and early 70's, we find camping back on the ground easier. Ian Dix ( Dixie ) has always made a good product, and he is easy to deal with. His company has made me several custom jobs of which are still in great condition for their age. ( i have no affiliation with this company apart from being a very happy customer). His products are not cheap, but he does produce a quality made all Australian product.
I cannot comment on the other product that you have mentioned.
In regards to a heater, my son in law just purchased a diesel heater which sits outside, and then he purchased a longer air heat tube to run into the camper, which leaves all exhaust gasses where they belong (outside).
Hope this gives you some help

Keep in mind that gensets are not allowed in national parks
you may need to go for solar and lithium batteries there are a number of suppliers that may be worth speaking to
I have found that Itech in WA are always willing to help (I have no commercial affiliation with them)
good luck with your research
Must add the best place to be today in this part of the country ( Snowys) is indoors!
Ed

I have an SC Ultimate 10 and it's stood up easily to 70 km/h winds and other storms. For even stronger winds, I'd probably support the top with a guy rope on each corner. I've had the SC for 14 years, still excellent and worth the initial expense. Southern Cross repaired some top stitching & a zipper for $100 (my rough handling, not their quality). I use the tent probably 30 times a year and it's still as good as new.

Last year I bought one of their cabin tents as I work interstate for several months and wanted more living space; it was an excellent home and very comfortable for five months so I can certainly endorse their products.

Don't know about the tent, but maybe google snow camping in Canada for some ideas on tent heating. There are some interesting you tube videos.