Yamaha is pretty awesome..... Not so much a fan of SeaDodo or of Kawasuckie....
You are obviously looking for something that is super sick fast. I am also taking this as you have considerable experience because if you don't you could find yourself totally fucked on one of these boys. 60+ MPH on the water is nothing to be looked at with impunity.
Do you have something against Honda? Just curious....
The open loop cooling system on the Yamaha could be an issue, ask your dealer if they have seen any big issues running them in salt water. Closed loop is usually a better standard when running in a salt water area. With the supercharged motor, on the SeaDoo, you really have to watch what type of gasoline you run in the motor too. If you get a little bad gas or some water in the gas you could be in a serious world of hurt when your motor wont run and you have to rip the motor down and replace all the seals and rings. Plus just because it has around 210 HP doesn't mean you can always get that 210 hooked up, and with a supercharger it is probably 210 at a really high RPM unless they have the crank way overdriven in which you would not want to run it wide open for very long. Which is probably why they have so many clutch issues. Kawasaki, never liked anything they made or make, dirt bike or water sport. Except the mule, but that was for work uses, and is not stock anymore.