I also have been accepted to CMU, but hope to get into UW as well!
However, I am actually leaning towards UW for a few reasons:
1. cost- UW is significantly cheaper
2. location- I love Seattle (location, food, culture, etc) and although I haven't been to Pittsburgh yet, people I know who graduated from CMU didn't give me the best impression of it
3. Better tech connections- Seattle has a lot more tech companies and opportunities for networking with people in tech than pittsburgh would
Also, the UW capstone project is also done with industry sponsors- great for networking and practical experience. Also, the IxD class seems amazing!
But what I like about CMU is the fact they make you code and they are slightly more prestigious.