Personally, I'd much rather have the B+ listed definition than the A-, and I am not alone.
IMO, the definition that you are using for B+ is more of a "collector's item" than the A- is. It would be if it were a classic car too.
The reason is because the B+ is still a "survivor" where the A- is a restoration. Slightly worn original is more valuable to a real pinball collector than one that has been restored with aftermarket parts.