As far as your concerns of VS blower in a dry climate.. It depends on the load calculation of what your sensible and latent needs are.. If you don't need much latent removal then the blower can be set up to higher cfm to remove more sensible heat and less latent..
You need a contractor that is familiar with Manual J(load calculation), Manual S(System selection) and Manual D(duct design). This type of contractor should be able to help you select the correct system and set that system up properly for your needs whether it will have a VS or PSC motor is up to you..
A VS blower on a "properly designed duct system" will be cheaper to run than a PSC blower and also will be quieter..
Make sure your contractor is taking the right steps to provide you with the comfort you are paying him for.. If he is using rules of thumb, time to find a true pro..