Seattle used to be a 64-team competition, but then we switched to a venue with bigger floorspace and but less seating room with two simultaneous regionals of 50-54 teams each. Last year was the first year of that, and after registration closed, they redistributed the teams by experience (i.e. by team number) to balance the rookie:veteran ratio.
As such (in no way condescending), it's somewhat amusing to see irritation at 50-team events.
I definitely agree with the district format as far as the logistics of the events and the increase in competition time teams get to experience, as well as guaranteeing a stronger pool of robots going on to CMP (it's a shame that 971 doesn't always make it).
However, and we're running into these issues attending just two regionals, the number of days of schools missed really stack up. It really isn't a major reason to justify not having the district format, though.
A bigger reason to justify not having the district format is the international teams. If Washington switches to a district format for Washington State (right now, we're at 90ish teams, plus a few inactive), where else would the Turkish teams that attend our regional go? A local team here started the team in Turkey, and having international teams (previously, Canada too when 1346 was still in FRC) really expands the scope of the experience for the students. Here near Microsoft and Boeing, we're all technology-spoiled, and the opportunity to talk to the international teams is a huge reality check--"Wow, we really take science and tech for granted!"
I don't know too much about the Californian regionals, but that is part of the experience I don't want to miss.