I've used both on dynamic effort work on the bench, squat and deadlift, and prefer the chains for one reason. They are MUCH easier on your joints. Bands make me hurt for a couple days in the joints, chains not so much. They both help a lot for development of strength threwout the entire strength curve, beginning to end of any given movement. I think Louie Simmons of Westside advised going 3 weeks of chains/3 weeks of bands and so forth. But, the bands are a hell of a lot easier to transport. Just throw them in the gym bag and go. Most commercial gyms give you the stink eye and WTF is he doing, when they see you lugging in a set of chains.