SELECT gives you two upgrades (if avail) for the same price. For example, I get a 'premium' car (Maxima) for the mid size price. United gave me bonus pts for being SELECT.
I had to ask for my SELECThood...even after qualifying months before. It took them at least a month to give me PREFERED, finally I got pissed and called. I ended up faxing in my info, snail mail route took over a month.
Hertz has better cars in my opinion....