How so?

More powerful, more addictive.

Not necessarily. Addictiveness is not directly related to potency.

From what I’ve heard, most addicts prefer heroin to fentanyl, even though it’s less potent on a weight basis.

They prefer heroin likely due to the fear of overdose. I pushed the button as often as the Dilaudid dispenser would let me after surgery. It's a pretty magical warm blanket. I understood the appeal immediately. All your worries melt away, and you're floating in a cloud.

Heroin produces a stronger euphoric effect than synthetic and semi-synthetic opioids like Dilaudid and fentanyl relative to its less desirable effects like respiratory suppression. Studies have shown that recreational opioid users prefer heroin to other opioids for this reason.