The Growing Dome is incredibly wind friendly as the wind simply flows around it. A rectangular greenhouse has a much larger surface area for the wind to push against.
The round shape also handles snow effortlessly because it allows snow to slide off naturally, so there’s rarely, if ever, that much snow pushing down on the green house. The geodesic structure is immensely strong, as it is made of triangles: the most rigid shape.
The curved surface of the Growing Dome allows for a very even heat input by the sun throughout the day. A rectangular greenhouse has a large flat area sloping south allowing a larger amount of sunlight to come in at mid-day, whereas in the early morning and late afternoon the light input is negligible.
Heat loss from any structure is proportional to the surface area of the structure. A spherical shape has the minimum surface area for the amount of floor space enclosed. The Growing Dome is much more effective at keeping the heat in on a cold winter night simply by having 40% less surface area than a rectangular structure through which the heat can escape.