With the Greeks, better architecture is the focus of the nation as each upgrade is given a refund of up to 5%. And every upgrade that is under 15minutes is free. After every age, the free upgrade limit is increased to five minutes.
Using the Greeks is important for people who value upgrading their Economy first before anything else since building is done faster.
The distinct unit that the Greek nation produces is the Companion, which has a good amount of endurance and hitpoints than most heavy cavalry. The upgraded versions of the Companion are the Royal Companion, Heavy Royal Companion, Elite Royal Companion, Stradioti, and the Companion Tank.