Do you mean old/new mold, or detailed/basic?
I'm not sure of the ages of the molds, but Hasegawa have one kit which is just the basic plane with movable geared swing wings.
Then they have another mold which has a lot more detail and options as well as PE. It's generally twice the price of the other (at least when i last bought one it was).
I don't know which one is the newer/older mold, but the last "detailed" one i built was terribly cast - it was full of flash that needed quite a bit of cleaning up.