Grill marks look appealing—after all our brains are wired to salivate even at the thought of a golden-browned, crispy exterior—but they're largely about aesthetics over flavor. When you use a grill pan, you're essentially only searing a fraction of your food's surface.
More Contact Means More Flavor
We intentionally make all our cast iron products, including our griddles, with smooth, machined cooking surfaces (like vintage cast iron). Surfaces like these allow a cook to maximize the Maillard reaction—a chemical reaction between amino acids and sugars that gives browned food its incredible flavor and aromas. Cast iron gets ripping hot and stays hot even as your food comes into contact with the surface.
Full contact of food with skillet = more Maillard reaction = more flavor.