[muertecaza]

Phoenix's is easy as it only has two counties:

1. Maricopa
2. Pinal

Maricopa has about 10x the population of Pinal (4,420,568 v. 425,264), so is clearly preeminent.

It wouldn't make sense to remove Pinal from the Phoenix MSA; San Tan Valley, the most populous area, is undoubtedly part of the metro, as are Queen Creek and Apache Junction, which straddle the line between Maricopa and Pinal.

Other municipalities are more debatable, like Maricopa, Casa Grande, Coolidge, Florence, etc. But I'd still consider those exurbs within the metro area.

The biggest problem in Phoenix is that they use county borders to define MSAs despite the humongous counties in Arizona. It creates some absurd results, like Marana, a Tucson exurb, being technically in both the Tucson and Phoenix MSAs, because a small portion of Marana is in Pinal County.

If the question was about CSAs, I would definitely carve off Gila County/Payson, which was recently added to Phoenix's CSA.