The sprayed stuff has about twice the R value but I'm still a little concerned about the long term affect of a water problem should one ever come up.
Water should not be an issue with a closed cell foam over any other of the choices. I know up here you do not have to run a vapor barrier with the closed cell.
It does cost more, but there is a savings to be had in the long term with lower heating/cooling costs. Granted our extremes are a bit different than yours. Temps here can sway 140*F with the seasons, so I'm not sure if it is as critical.
Personally if I were to build a house today, (I know a garage is a slightly different story...), I wouldn't consider anything else.
[edit]- The noise suppression from the spray in is also very impressive.
