Decide whether you’re going after less income tax ultimately or less out of pocket expense. (Out of pocket being not only your license plates but all other expenses including sales tax, vehicle use tax etc. ). A dollar is a dollar doesn’t matter if you’re giving it to Mc Ds for a cheezzburger or the dmv or the irs.
While WA has high general cost of living in some areas and high sales tax and a bunch of gotchas when it comes to use tax, it has no income tax. I could argue that I can live cheaper here than some state with half the sales tax and super cheap license plates.