E&P has only 2 editions 1st and 2nd. They correspond to Catan Editions 4th and 5th.
The difference between E&P 1 and E&P 2 is that the standard terrain art matches either Catan 4 or Catan 5. It is otherwise the same.
Note that Catan 4 was produced using two diffrent manufactures. The original (for most of the printings) used thinner cardboard but the quality of printing and cutting was excellent. When they started producing E&P they thought they needed thicker cardboard and switched everything over to a different manufacture. The newer Catan 4 have thicker cardboard but poor printing and cutting. Catan 5 is just the same as newer Catan 4 except they changed the art.
Thanks for the reply. So is there any way of knowing which is the old and which is the newer stock of the 4th edition prior to purchase? I.e. Anything on the box to distinguish?