Sedan/coupe preference over SUV so maybe that’s why I’m biased in this view but I’ve had at least a Prestige Series P4 class or higher sedan, at each of SEA, ORD, PHX, and LAS over the past 6 months and 15ish rentals. Only maybe 3 or so ended up being PCARs while the rest were Infiniti, BMW, Mercedes, or American Muscle.
These upgrade would never be found for free at Avis... National at SEA is comical; and all other times Hertz has been cheaper and my first pick.