I am not qualified to talk about this matter, but I can read and understand most of it. In my very unique opinion, the venture between Cornell and Garcia seems to have a big marketing profile.
There are other options, and If I ever have the resources and time to make a high latitud passage, like Cape Horn, I would consider the options I found here: Sirius-Werft Plön | 40 DS | 40 DS
Yes sure, Cornell and Allures are doing joint ventures from some time but Cornell after making several circumnavigations in different kinds of sailboats discovered the OVNI 43, made a circumnavigation in it (70 000nm) and declared that it was the best voyage boat he had ever sailed.
Then Allures appeared on the market and it is the same kind of boat, lighter and with a better stability and Cornell soon started to be interested. Their relation comes from his interest in the boat.
When time comes for a new boat (and probably he was thinking about that from the beginning) he asked Allures for big modifications on the Allures 45 and they decided to make a boat for him using the 45 hull, that is made by Garcia (Garcia belongs to allures and all their hulls are made there). For commercial reasons they decided to call it a Garcia even if Garcia is only making bigger boats.
This is his dream voyage boat and the least we can say is that the guy knows one or two things about it
I know well Sirius (this thread started with a Sirius) and even if it is a great boat it is a Luxury cruiser, not expressly designed as a voyage boat. Not saying that it cannot voyage only that it is not as good at that as a standard Allures 39.9 for instance, much less in high latitudes where the Aluminium offer a superior protection against ice.
Also in the case of any problem these type of boats (Aluminium centerboarders) can be beached for repairs, offering also an additional protection against grounding. Final a aluminium centerboard with an adequate ballast is one of the best boats to survive bad weather (it has a great dynamic stability).
the Garcia 45 is a reinforced boat and expressively built for an expedition. I am sure that it is more resistant than any production boat (almost 3t heavier than a standard Allures 45).
Regarding the Sirius 40 they have that project for years (and also one for a 43 that they seemed to have abandoned) but it seems that they have not find yet a client for the boat. Maybe you
The boats are very nicely built and with the better interiors you can find on the market, regarding quality and use of space. Unfortunately the prices go in pair with the quality.