All "other" things are never equal and both mileage and age change that inequality no matter what it appears - like tires I cited for instance.
I doubt there are any warranty considerations for anything 8 and 12 years old.
In Class Bs there have been significant improvements in quality in the past decade. The 8 year old B falls within those improvements. If it were a Pleasure-way the simple improvement of intelligent battery charging would have occurred just 8 years ago. Winnebago didn't figure that out until 2014.
To me though, it is clear since it was asked. 8 years is always better than 12 because that 60,000 miles is not that significant for a Class B.