Weight savings over the iron. Plenum style. We are about to put a Performer on a9 Barracuda's 340. That was chosen over the Air Gap due to the climate being more temperate and the car is driven when it's pretty cold out.
I love my LD340. Great for a cruiser or mild street/strip.
When you have an Airgap style manifold whether dual or single plane, a carb with annular boosters really aids fuel atomization.
I live in Alberta which has cool temperatures compared to a lot of the US. My Performer 600 functioned well on the Airgap. That said and the engine apart, I got boosters for the AVS2 650 to put in it and a 1906 calibration kit.
Here a nice summer day is 70 to 75°F. Normal is between 60 and 65°F.
Now winters, that can go down to -40° while normal is -10 to -20°F