I remember when PAX announced their first convention, and it was going to be a week before ours... I was so pissed! Ya see, I'm a really big fan of Penny Arcade, and I had even entertained a notion we could get them to come down as a guest at our con one year.
For the record, we announced our date first in 2004, so they totally stole our thunder...
This year, when I heard that they were on the same exact date, I screamed bloody murder. See, I was planning to go to PAX this year, a ha ha ha ha ha... crud...
As much as I love Kumoricon, man, if I lived in Seattle, I don't think there would be much choice (actually if I lived in Seattle, I would have already gone to Pax the past 3 years, gotten bored with it, and then come down to Kumoricon this year :-P)
But, if you live in Portland or Oregon, just stick with Kumoricon! Go to PAX next year when they don't overlap.
I've heard a lot of different stories about PAX. It's very very large. People can get bored there easily, unless you have something specific to do there. The people who run it actively are trying to not make it E3, just a consumer event. It is by fans, for fans. It is not about having displays of the latest technologies (though some companies do bring new software there anyway), it's about playing games with other people who like to play games.
Okay, I'm totally rambling, but whatever. I hope everyone comes to Kumoricon, but I understand if you are a gamer at heart, you may find the gaming mecca in Seattle :-(