A vented grooming brush is smaller and built for finishing and root lift; a vented paddle brush is wider and better for detangling and blow-drying thick or long hair straight.
The vented design lets heat pass through and disperse rather than trapping it against a solid back, which reduces the heat exposure your hair gets during blow-drying compared with a non-vented brush.
The Vented Paddle Brush is preferred for thicker, longer hair as its wider head and firmer bristles are built to detangle thick, long hair and smooth it during a blow-dry.