OAK and PHX are pretty much the same size and the lines are very similar. I could be wrong, but that's what I gather having been based at both. OAK will likely have more west coast flying (which is nicer in the summertime... SEA, PDX, OAK, SMF, GEG, BOI, SAN, etc. are much better in August than places like MDW, MCI, HOU, etc. Think level 5 storms with tornados.

) Otherwise the lines are pretty much the same with 3 and 4 day pairings in the mix. Both bases are very commuter friendly from So. Cal. If you are near ONT or LAX you'll have multiple flights to choose from all day (BUR and SNA offer fewer choices.) ONT to OAK or PHX is probably the easiest commute in the world. You'll have about 13 flights/day (fewer on Saturday) to each city and the flight is aout 1 hour either way. (LAX is about the same) PHX has the advantage of using HP from any of the four So Cal cities, and they are very nice to us with a multi-seat jumpseat agreement.
PHX has some advantages over OAK. For one thing, you are less likely to get "capped" by someone walking around the commuter hotels in the PHX area. In OAK, best be careful walking around that garden spot.

The hotels in PHX are more available and cheaper than OAK. You'll save about 10 to 20 bucks per night in PHX. Disadvantages to PHX... you'll bake during the summer, be sure to drink lots of water. Also, you'll want to see a dermatologist more often.
Overall, both bases are great with excellent people to work with, but that can be said of any of our bases. PHX is getting a new crew lounge. Word is we will have a putting/chipping green, swimming pool, and a full size poker table to accompany our big screen TV!! Although that may be a rumor.

Concentrate on getting the job first, then worry about bases. Good luck.