In the fitness industry there are many different opinions of what are the best exercise to do. On the other hand the anatomy of the body tell a different story. Many people use a deadlift as a back exercise but if you understand the anatomy of that area of the body you'll begin to understand that there is one way of training.
1. All Deadlifts always includes hip extension
Hip extension maintaining the natural curves of the spine in a bent over posture and then standing up straight like in the picture to the left. Although the exercise will activate the spinal erectors they aren't main muscle working. They are a much smaller and weaker muscle than the muscle of the hip, all lifting should be left to the big muscles of the hip.
2. Gluteus maximus is the hip extension muscle
Leonardo Da Vinci knew this in the 14th and 15th century when he said "The principal and the greatest and most powerful muscle in man are his buttocks - these are of marvellous strength, is dominated by the force exerted by a man when lifting weights." Nothing has changed in 600 years and we will increase the performance of our whole body if we use the deadlift as hip and hamstring exercise.
Spinal erector run the length of spine and do cross onto the pelvis, this means they will be active as you go from a bent over posture to an erect one. Although they are only assisting in the movement and not primary movement creator. The erector spinae muscles primary role is to maintain the correct posture of the spine not move anything.
4. The core work better as a whole than as parts
Any good performance coach know that the core muscles work best together, if you split them up and do exercises that work them individually you in fact diminish their performance. Exercises like back extensions, sit ups, crunches, side bends or twists don't help your core. They might make the individual muscles for tolerant of fatigue but that doesn't mean your whole core will benefit.
Use the Deadlift as a hip and hamstring exercise