Hi,
I thought I chime in again here. I bought leaderfins Carbon Waves medium stiffness some time ago und used them frequently in the pool since. I really like them for pool training, but for greater depths, say beyond 25, 30m, they are a bit too soft, at least for me. I use C4 Falcons 30 for deeper spearfishing and rope diving, but was never totally happy with them. Now I got the opportunity to try the "hard" version of the Leaderfins Waves Carbon, and I liked them very much too. There is quite a difference between "medium" and "hard", and I think the "hard" here is rather what you actually would expect to be a "medium" normally, while the Leaderfins "medium" feels pretty "soft" :duh. Anyway, compared to my Falcons 30 (which correspond to a medium stiffness), the "hard" Leaderfins are almost of the same stiffness, just a bit softer maybe. But they are very comfortable, very precise, very reactive, they give you good power, and after comparing the two intensely in the water i felt that the Leaderfins work better for me than the Falcons.
So, just for those of you who don't have the opportunity to try both, medium and hard, consider that the medium stiffness is pretty soft, and what they call hard is a good medium, compared to other brands (for example C4, or Cressi Gara fins and Omer - the ones I used so far).
By the way, C4 is not at all "another world", it's just the first brand that made carbon blades, it hast a good image and is very expensive. But in the meantime, there are many other manufacturers that produce excellent carbon fins. I am convinced that the differences between carbon baldes of different brands are minimal. It all depends from choosing the right stiffness, fin shape and a really well-fitting, good footpocket. Then it gets less important wether the fins are "pure T700" carbon and have "C4" written on them or are a Leaderfins Wave model for half the price. The only thing that counts is how you like them in the water. Therefore, if ever possible, try before you buy!
cheers,
ivo