Portland gets about 200 more hours of sun a year according to the official sunshine statistics... which stopped being taken in 1995 for some reason. That is at the airports though. Walla Walla and Spokane also have sunshine data that seems to indicate that the Columbia Basin actually isn't much sunnier than the westside overall, partly because the winters are so inversiony.
Sunshine really starts shooting up south of Roseburg or so. There isn't really any accurate sun data between Portland and Sacramento but number of precip days tells a similar story. Roseburg gets about 140 a year, Ashland about 115, Mt Shasta City 100 (less than Spokane), and Redding about 80 (about the same as Yakima or Tri-Cities).