My general answer to the question is yes.
At my local airport, Executive tends to have the best selection. And, I have never yet had National balk when I do a self-downgrade to a more economical car, as long as I was paying the higher price.
However, right now I have 6 or more rentals a year that are for the most mundane reasons(where even an Aveo will do
). Even though I cannot earn airline miles at Enterprise, having the Enterprise rentals count toward status with Emerald Club has been very helpful.
So, I would not be really keen on paying for something that I would likely earn over a year anyway.
P.S. Even now that I have Executive status, my decision on which company to rent from can still be swayed by a big airline miles bonus.