@Saki: From my personal experience, I find both cons to be fun in their own ways. I still can't decide which one I favor the most though.
I like Sakuracon because of the ideal location (at a convention center) as well as where it's situated: in the middle of the city, literally right across from the Sheraton which I've always stayed at since my first time going. ^.^ There's also a ton of stuff to do. The Dealer's Hall there is AMAZING. <3
Now, I like Kumoricon just as much because the people there seem more laid back and friendly, and you feel more personal with them than at a super large con like Sakuracon. I'm assuming it's because Kumoricon has a smaller community, although it has been growing rapidly like whoa.