As for which is best for you, well try both and see what you like.

Harder dampeners are better for 3D, they help keep the blades and the boom from becoming one during more violent manuvers. They offer more crisp cyclic response as well. The down side is you need to run a higher head speed or the head will wobble.

Softer dampeners are better for general sport flying and scale and they run lower head speeds w/o wobbling.

Think of it like a car suspension, a tight suspension lets you feel the road and have very precise control if you're racing but it's not very comforable for cruising.