Is it true that a forged blade can shape a shot better than a cast cavity-back?
Cavity-back clubs are designed to minimize the negative effect of off-center hits. They should be more stable at impact so off-center hits will fly close to the intended target.
However, if you’re working the ball, you don’t want straight shots, you want fades or draws. Well, just as your mis-hits are going to be worse with blades, your intentional mis-hits are going to be easier with blades. Most tour pros play with blades because (a) they don’t miss the sweet spot, (b) they like the feedback blades provide and (c) they prefer that type of shot to reach tight targets.
This is not to say you can’t work a ball with a cavity-back iron, but most of us need to concentrate on hitting the ball straight first. Working the ball requires an extra calculation (how much left or right of the target do you aim, and how much do you turn it to get it back to the target).
Best to start learning how to hit the ball consistently where you want it to go, then work on shaping your shots.