I own both the SS2 and the Hilleberg Kaitum 3, which bears more than a passing resemblance to the CB3 but weighs double and is primarily a winter / expedition tent. The CB3 has some really interesting design features and optional extras, and I was tempted for a short while to have it replace my SS2. However, in the end I didn't and that was down to the following considerations for my intended use:
– side vs end doors (in a midnight pee break, the former is less likely to disturb the partner trying to sleep)
– vestibule size and arrangement (bigger, easier to stash pack(s) to one side and not trip over it; with the end door the entire width of the vestibule is your entry/exit)
– cross ventilation (in summer especially, the shorter distance for air to move across vs down the length of the inner benefits all)
– detachable / swappable inner (can't go floorless with the CB3; no option for semi-solid doors)
– wind-shedding angles (tunnel is very aerodynamic on one axis, passable off that axis but with a lot of flysheet movement; swirling winds are less noticed in the SS2 due to the multitude of angles)
– site selection (SS2 is a wide tent, but CB3 is a long tent with relatively short vestibules which may rule out a lot of sites depending on where you camp)
I love my Kaitum 3, but it's a lot more liveable in winter than for the rest of the year. The larger vestibules do make for a very long shelter, but they offer more well-ventilated options where gear can be stored out of the way than in the CB3. It's easier to pitch the K3 in snow than on dry ground due to its large footprint (stomping down snow is easy to create a level site).
