Weight may be weight, but it's the leverage required to lift/move any given weight. Possible that this is the difference between a exercise "machine" and the common BB/DB. Also lifting a weight through air, as dips & chins, set in motion another leverage example.
When lifting old style globe weights, I found the looser a grip the better the bar could be handled. Too tight a grip puts undo stress on the wrist/forearms/elbows. Just my view, that's all.