If you mean PhD program in CS when you write “grad school”, either should be fine; consider your subarea interests and what each school offers in terms of upper level courses and undergraduate research opportunities.
For PhD programs, reputation / ranking / prestige in major as viewed by PhD granting departments (whose views may differ from that of the general public and each other) is the more important aspect, although the difference between these schools (with Washington being ranked higher in CS) probably is not significant enough for you to worry about when choosing an undergraduate school.