That's the take of a pretty cool little Score Predictor device installed over at the MLSsoccer.com site.
This isn't a fan survery, btw, but rather a mathematical calculation.
However, before trying to book a flight down to Vegas today, you should note that the Score Predictor seems to be something of a statistical cousin to the Castrol Index, which ranks Seattle's Alvero Fernandez, New York's Thierry Henry, and Kansas City's Chance Myers as the three top difference-making players in MLS.
(That said, the MLS Cup Predictor gives Seattle the second-best chance of winning the cup, behind only LA.) (What a shame MLS has created a playoff structure that will prevent them from meeting for the cup.)