I called about this on Friday specifically because I have about a week left before my window expires. Here's what I got:
Valet is offered at no cost. Ranger is $100 per incident unless you buy the pre-paid package.
Where they are different is this:
Ranger is someone coming to fix something on your car wherever you need them (like home or office). Valet is just bringing you a car for a loaner and taking your car back to the service center for any service that will take 4 hours or longer to fix. If it's something that takes less than that, then valet is not offered. You would need to take it to a service center if you don't do the ranger service.
So, let's assume there's a problem that can be fixed either at your home or in a service center, but will take more than 4 hours (scheduled time it takes for that type of repair). Valet option will bring you a loaner car, drive your car back to the SC, and then bring it back when it's done. Ranger service will bring a tech out to you to fix it. I didnt' think to ask whether it could still include a loaner, so that would be good to know.
If it's an issue that takes less than 4 hours to fix, then valet is not an option. Ranger service would send someone out to fix it. Without it, then you'd have to take it into a service center and wait for it to be fixed.
And a caveat on all valet. It's as available. If there isn't a car available, then you may have to go the Enterprise route. If you have any other questions, Call ownership. It's what I did on Friday afternoon and got to talk to someone who answered my questions immediately.