The difference between Greek and Roman coins of the early empire that I find interesting is the relations between the metals. Greeks had big silver coins with fractional parts and many very ordinary small bronzes. Romans had small silver coins and some really impressive bronzes with relatively few small bronzes until the late period. Collectors think of Greek coins as expensive but there are thousands of very cheap bronzes from quite a wide range of centuries. Save a few rare medallions, Romans did not do big silver unless you count provincials. There are large Greek bronzes but not nearly the variety there is in small Greek or large Roman. The Romans used gold more than the Greeks did so they had less need for big silver. A normal high end collection will have large Greek silver and large Roman bronzes. Of course both have gold but those are out of the reach of many/most collectors.
I'll contribute a couple of modest Greeks: Alexander III, bow and club type; Antigonas Gonatas, Pan erecting trophy. Worn and rugged, but respectable, and satisfying in hand...