I think you'll probably get a lot of opinions on this, but I think it will ultimately come to factors unique to your situation. Both schools have great programs and reputations and I don't think you'd be doing yourself a disservice by choosing either one over the other. Little factors I can think of though:
I believe that you said somewhere on here that you currently live in Atlanta? Have you spent much or any time in Seattle? I was considering UW (it's a great school!) so when I flew home from the Peace Corps I made a layover in Seattle and planned to stay with a couple of returned volunteers. They had all talked about how awesome Seattle was and how much I would love it. I got there and they told me how lucky I was that I was there on such a nice day (I thought it was pretty dreary compared to the souther sunshine I'm used to - I'm from Tennessee - but I knew to expect that there). I had great tour guides and saw some cool stuff, but I really really disliked Seattle (don't tell my friends there, they would disown me). Anyhoo, you may love it there, but it would be worth it to visit for a few days if you never have because being miserable where you live can affect your school work, social life, etc. (This is not to hate on Seattle, I would say it's smart for someone to do this for any school in any city).
Where do you want to work? I'd take a look at the organizations that both are affiliated with and see which of those places you would be interested working, if you make a Rory Gilmore list you may find that one school has several more affiliates you could see yourself employed with than the other. (Not that you can't get a job at the affiliations of another school, but when you're choosing between two great programs a small advantage could make the decision for you). Even places the schools don't work with but are in close proximity to the school, if you find a place or organization you might want to work with that's based in Seattle then going to UW would give you an opportunity to try for an internship or summer work there (and vis versa for Atlanta).
I'd also look at timelines and financial aide. I didn't end up applying to UW because of how I felt about Seattle...but I know that Emory is generally a 4 semester program where many others are 3 semester (maybe UW is?). This can be seen as a pro or a con, it keeps you out of the work force and paying tuition an extra semester, but it also gives you a chance to take more courses and doesn't rush your learning. Also is there a large tuition difference?
"Vibe" from the school was also something I thought about, when you email each school do they respond in a timely/personal manner? Do you feel like you click with staff/faculty you have spoken with? That was big for me, I've decided on Emory, and part of the reason was how helpful the faculty/staff were, they always emailed me back when I asked questions and often initiated contact with me about things. It felt personal and I clicked with them (rather than just feeling like a SOPHAS ID number). Other people may have not gotten the same vibe from Emory or may have gotten a better one at another school, another point that would be your perspective and not others'.
Anyhoo, like I said, these are just things you could add to your list (if you haven't already) and are small things that I would probably nit pick on my list as well
Good luck!
