That's subjective,and really difficult to say.Like saying which cars brands & years are the most popular to purchase.
There are fans & followings for nearly every single oil company produced throughout the years.
As far as pumps go,some only look for them used & molested & in need of repair,to tear them down and completely restore all nice & shiney.While others seek them used,lightly molested,and leave em that way.
Although there are some on this site that do too,I'm one of a minority on this site that collects gas pumps & their history.
I suggest you register & become a member of
http://oldgas.com/forum/ubbthreads.php?ubb=cfrm
Quite frankly,the most informative gas station forum & related objects you can find on the web.These guys have been everywhere,and seen nearly everything there was/is.Their various annual endorsed shows around the country are highly attended & extremely informative.They love people who try to stump them with a question or object..it's their forte to find an answer.
Nearly every single gas pump/station question you have,can be answered there,but it may take a few days/weeks,as many of those old guys who worked around ethyl,don't ride a keyboard daily/weekly.