GLORY AND DEATH! SPARTANS WILL NEVER SURRENDER!
Co-King of Sparta and a titan of Greek history, King Leonidas I was the leader of the Spartan coalition during the Second Greco-Persian War and led the Greeks to immortality at the Battle of Thermopylae. While ultimately losing the battle and letting Persian forces enter an abandoned Athens, his heroism led to the deaths of over 20,000 Persians at the cost of only 4,000 Greeks, a ratio of 5:1, and arguably led to some of the most major views of European identity and the future "unification" of Greece thanks to the post-battle writings of Herodotus.
Spartiátiki Timí -
Spartans are born and die around a culture of supreme honor. Spartans will quite literally never give up, and they would rather die in combat than live to be an old man. Spartans will face off unstoppable odds and seemingly unwinnable battles to simply die in combat as a hero. "Come back on a shield or don't come back at all."
While only having 300 hoplites, the actual number of Spartan troops at Thermopylae was 1,200. The total number of Greek troops was around 7,000, but that's a bit too excessive.
Stronger Armor -
The bronze armor and shields of the Spartans are stronger than the predominantly iron and crude steel weaponry of the samurai. The Spartans also have shields --- pretty damn good shields, at that --- which were frowned upon by samurai culture.
Stronger Men -
Spartan warriors were, on average, extremely muscular and strong due to their warrior upbringing. Compared to the samurai, a single Spartan could probably beat a few in an arm-wrestling contest.
Ancient Tactics -
Sparta flourished in Antiquity, and as such their tactics are built around ancient combat. They have never thought about, let alone encountered, modern weaponry.
Limited Armor -
Spartan armor primarily consisted of an armored skirt, large shield, breastplate, and helmet. Major parts of the extremities, such as most of the arms up to the shoulders and legs up to the knees, are left exposed.
Lack of Range -
In contrast to the guns, bows, and artillery of the samurai, almost every Greek city state abhorred the "cowardly" and "distasteful" nature of the bow and arrow. Lightly-armored slingers and archers may exist, primarily to back up the phalanx, but the bread-and-butter hoplites and the Spartan rank-and-file will not use ranged weaponry on principle.