Hi Will,
Regarding Monsoon 2008 yes it was spectacular. My second best year ever, for lightning and haboob photos, just behind 1999.
I guess it depends on one's perspective. There is also a Facebook page called "I survived the Arizona Monsoon 2008" or something to that effect. There was a lot of heavy damage with the August storms of '08, so I'm assuming these are people talking about the effects.
As for whether Tucson or Chandler would be a better chase-base, that depends on the time of year. If it is early, June/early July, I would say Tucson. By mid July the monsoon is up in Phoenix and I think PHX is more favorable for more chances for night storms. Chandler is good because it is in the SE Valley and that tends to get hammered more often.
Either Chandler or Tucson has about equal access to the Central Deserts.
Re: La Nina... it seems that La Nina years are hotter and drier, but that doesn't seem to make a difference to me because I'll go anywhere in the state for the lightning. If the deserts are dry, I'll go to the Mogollon Rim, which is a pine forest. The Rim is a lightning magnet. If the northern half of the state is dry, then I'll head to Benson/Willcox/Tombstone or Bisbee because the SE corner of the state gets the most generous monsoon flow. There are many factors, not just synoptics too, that help generate storms. I could write a huge page on favorite hot spots, but let me know if I answered your questions
5 months and counting!