Who would be better if Juluis Caser led his armies to take control of Greece. What if his armies came across the Spartan army. Who would be better in that battle, or who would be better in any case?
The Romans would destroy the Spartans. They had better technology, technique, and numbers.
The Romans would just use their catepults to kill a significant number of Spartans all on its own.
Plus, the Romans had a "wedge" technique that they used to conquer other countries.
Rome wins. Sparta was a city-state of Greece. Rome kicked the crap out of greece.
The Romans already beat Greece, long before Caesar.