When use a Marinade and when Spiced Oil? To better understand the subject, one should know that marinades are opaque, covering the meat's surface.
Therefore, use a Marinade for stir fry's and marbled meat chunks.
Spiced Oils, in contrast, are more transparent, leaving the meat's structure visible, as shown in the above picture. The herbs and spices within the Spiced Oil "float" on the marinated meat, remaining clearly visible.
Therefore, Spiced Oils are best with larger, lean meat chunks, such as steaks and lean meat strips.