There are only a few  Basic Berkeley jets , Insert pumps (12je's and f's) which are "hull specific" meaning they require a certain type hull design  and 12ja, b, c, g, etc all of which are very similar in design and share (for the most part) similar if not the same parts . They all work basically the same and to make them "better" is a matter of Bowls, bolt ons and internals (Upgraded shafts , impellers etc and blueprinting  Tom

PS if forced to choose one above all the rest it would likely be a late 12 jG

I am a personally prefer older pumps, I have a 12JB in my little boat, there just seems to be more material in the suction housing around the thrust bearing and the quality of the aluminum seems to be better IMHO. They are however getting difficult to find.

Personally I think the differences are small enough where it barely matters at all. It's boils down to quality of the shaft, impeller and bowl as far as where the rubber meets the road.

GT