For the most part they are the same diameter; the nubbed intakes are bigger around but a possibly bit more restricted it seems. The differences come mostly from the internal passages I'd say. The Twist and DLXs are mostly just a straight, open shot where the others have various bends and tight spots.
I'd rank this random sample from tightest to most open: DW Punch v1, SBL Flip Brick, SBL Runt, DW Switch, DW Punch V2, DW DLX/Punch, SBL Twist, DW DLX One. The DW DLX Pros are pretty open, too. The NOVA I'd put between the Runt and the Switch.
In use, none are really hindered by their relative open/tightness, but the Flip seems noticeably tight and the Twist seems sometimes almost too open depending on the pipe. Both the Punch V1 and the DLX one are not as problematic as those they sit beside, not really sure why.
