We have a Clipper II with both fixed float and regular skid gear. The Clipper has extra anticorrosion protection, an additional bit of stabilizer on the empennage, position lights on the rotor mast fairing, and an second (white) anticollision strobe.
While the Robinson advertising calls the fixed floats "fixed utility floats", the POH tells a different story. Water landings are not recommended except in emergencies. Depending on the weight of the helicopter, when the Clipper is floating the water level may be near (perhaps at) the door sills.
It is a great helicopter, and having floats sure eases your mind when flying over all the lakes we have up here! Changing the skid gear takes well under an hour as long as you have the hoist fitting and a big enough hoist or crane.