Took CS from SEA-PDX last month; taking Cascades same city pair next month.
Agree with avoiding the Northbound Starlight, but found that the SB train worked well - lowest bucket roomette add-on was $50 - or $25 each since there were two of us traveling. Well worth the upgrade over Cascades business class, considering that we got sparkling wine, a choice of two lunch options (we did the traditional dining car), private room (which we really didn't use) and access to the Pacific Parlour Car.
Either are good choices, so I'd go with what works best time-wise.