The problem with most machine preacher curls compared to their free weight counterparts are generally short in focus, meaning the hardest part of the movement is near the top where your elbows are already bent. This is not favorable for the biceps because, compared to the other muscles that also bend the elbow, the biceps have the best leverage to bend the elbow in the lower part of the range of motion where your elbows are more straight. This is why free weight preacher curls are generally bett