SR.com: By the numbers, Spokane's still No. 2 : "Even without counting three recent annexations, the city of Spokane holds a 600-person lead over perennial second-city rival Tacoma. Those annexations %u2013 totaling 1,469 people %u2013 will be added to Spokane's total next year. So it looks like Spokane has a lock on the title, at least for now."
Of course, when we stop treating it like a competition, it will cease to matter. Tacoma is an entirely different city, and is treated as a bedroom-community-of-Seattle/city-in-its-own-right/how-did-I-end-up-here sort of city, and Spokane is where everybody from Ellensburg to Missoula goes for Heart surgery.