stopping for a single night - rest area or rv park?

I have done both. Really depends on the pace you are traveling at as well as what's available.
I prefer the CG simply because it's more relaxing. However it requires staying more time in general to be of value.
Walmart rest areas are an OK alternative if your in a rush.
I've sort of concluded there is no point in being in a rush if you're on vacation.
It really not about hurrying to your destination, but it's more about maximising your relaxation time.