The Puck Pro is a huge leap over the Puck (and thus the Puck Air). It is my backup computer, even. It has for a non watch design a reasonably slim design, and it can do multiple gases.
I really did not like the Puck at all, and used to use the Oceanic Puck style wrist computers for backup,but I really like the Puck Pro. It has a bunch of little touches that show someone at the company actually uses it, and they are not just throwing out a product.
It is like all one button computers a pain to change setting on, and when people play with mine they often can make changes to the mix and whatnot, but that is a problem with all single button computers.
(All I know about the Cressi Leonardo is from reading about it, but it looks like it shares the form factor with the previous model that five different companies all used (DiveRite Duo/Trio, Tusa whatchamacallit, Cressi whatever etc.). If that's the case, it is slimmer than the Oceanic wrist warts, but nowhere near as sleak as the Puck Pro.