The US Census says that, as of 2009, Seattle edged out Portland in commuting by transit. Roughly 8.1 percent of greater Seattle commuters rode transit to work in 2009, compared with 6.1 percent in greater Portland.
Focusing on just the cities themselves, rather than the entire metro areas, the difference was even starker: 20.8 percent of Seattle workers commute by transit, compared with 11.6 percent in the City of Roses. (All numbers here are from the Census American Community Survey website, and are compiled based on where people work rather than where they live.)
Of course, we know that these numbers can’t possibly be right: Portland has a nice train, but until mid-2009 greater Seattle had only a few measly miles of light rail. And everybody knows that trains always beat buses. </snark>