Dear Thomas and Frosty,
I mean by the coil spring hammer, the one in these links
https://goo.gl/IB3yCQ
https://www.youtube.com/watch?v=q3nUCwQ6JQk
And I mean by the leaf spring hammer, the one in these links
https://goo.gl/cE7tQB
https://www.youtube.com/watch?v=KPZSYzDCRVE
I mean by "better", I need to compare them in according to cost and easiness to manufacture and build