Tenderizing

• Marinating, or steeping meat in acidic liquids such as fruit juice or vinegar, can help to tenderize meat. The liquids seep in between the fibers of the meat and help to break down tough connective tissue before the cooking process even starts. Rubs can have a similar effect, but only due to the manner in which they are applied. Vigorously massaging the rub into the surface of the meat can also help with tenderizing, but only if done with sufficient force. Because of this, rubs should generally just be sprinkled onto fish. Their delicate structure can be destroyed by the rubbing action, causing the flesh to become mushy and mealy.
  
  

Blackening

• Blackening is a popular technique that originates from Cajun cuisine. Dry rubs, pressed onto the outside of meat and fish, are deliberately burned onto the surface. The carbonized layer of spices protect the food from the direct heat of the skillet or grill, keeping it moist and increasing the penetration of the rub's flavorings. Wet marinades will generally caramelize onto the flesh before they burn, and the thin, liquid coating provides less coverage than the dry powder, so trying to get it hot enough to blacken will likely just overcook the meat.
  
  

Time

• Traditionally, marinades are applied to the meat some time before cooking, and sometimes the meat will sit and steep in the liquid in the refrigerator for hours, if not overnight. Rubs don't require this degree of preparation and will not be impaired by being applied to the meat directly before cooking. Some cooks apply rubs the night before, but this is more to help them adhere to the surface of the meat rather than to allow the flavor to penetrate. The tenderizing effects of marinades are also based on a chemical reaction, which needs some time to process..
  
  

Cooking Methods

• Marinated foods will generally perform well with a broader variety of cooking methods. After marinating, meat and fish can be fried, baked, roasted, grilled or steamed, with little variation in the quality of the result. Meats covered in a powdered rub generally benefit from direct contact heat, such as pan-frying or grilling, as the flavorful outer crust is one of the main reasons for applying the rub in the first place.