US2 from Spokane to Wenatchee mostly crosses flat wheat fields, with possible side trips to Grand Coulee dam, Banks Lake and Dry Falls. You can also take WA155 from GC to Omak.
From Wenatchee, US2 passes through orchards, Leavenworth, and into the mountains. The drive over Stevens pass is scenic. Traffic picks up as it passes through towns like Sultan, Startup and Monroe.
WA20 after crossing the Lake Roosevelt at Kettle Falls climbs to Sherman Pass, and continues through low mountains to the intersection with US97. Sherman Pass is higher than the Cascades passes, but over all these mountains aren't as scenic as the Cascades.
WA20 through the Cascades (after Wintrop) is somewhat more scenic than US2. Area Chambers like to promote a loop trip that includes both US2 and WA20.
http://www.cascadeloop.com/