Are U-locks really more secure than chain or folding locks?

For a given price and weight, U-locks generally test better against bolt cutters and leverage attacks, and across mainstream reviewers and cycling subreddits they remain the default recommendation for daily commuting. Heavy hardened chains can match or exceed U-locks in raw security but are heavier and harder to carry. Folding locks sit in the middle: more flexible and easier to mount, but reviewers note they are typically easier to cut than a comparable U-lock.