[willy]

They are all good motors, if you are insistent on extended range get any one of them to be honest with you. A good running brand new under warranty Yamaha 150 carbed two stroke would far and away be my first choice among the engines you mention. The difference in fuel economy is not that great. If you are going to do like a lot of fellows that have the cash to do it, and buy a new engine before your warranty expires, then I would go with any one of them.
If you are going to keep the motor after the warranty expires I would trade a little fuel economy for the superior reliabilty of the Yamaha 150 carb.
Just my thoughts on it.
As a matter of fact if I can raise the dough, I am planning on selling my 18 year old trouble free Yammie 150 for a new version and selling my current one for some cash to pay for install and some accessories.
Let me know which one of the engines you mention you think you will get 18 to twenty years on, with basically the cost of oil and fuel and the ability to fix any of the much simplar issues that come up, if any come up that is. None have on mine.
Never mind we already know the answer don't we.