The short answer is both. The longer answer is far more complex.

'The Greeks' were not a monolithic entity. Nor was their military innovation static in the 300-odd years during which Rome fought with cities and nations that laid claim to Greek heritage.

The Macedonians, and the other Successor States of Alexander's Empire (Syrian Seleucids, Egyptian Ptolemy dynasty, etc.) generally fought with the longer spears you describe with armies that drew inspiration directly from Alexander the Great's armies and tactics.

The Greek City-States, of which there were many that dotted the shores of the Mediterranean, would often still fight with the shorter spear you describe (although it was often more like 8' or 9' in length). But depending on the era, some of these states may have fought with long, pikes like the Alexander-style infantry. And later on even the Alexandrine Successor States began to implement reforms that moved away from the pike altogether, to lighter and more flexible infantry.

If you want more detail on anything specific I'm happy to provide it, but I don't want to dump a wall of text on you if you aren't looking for it.