Do y'all remember that show "Deadliest Warrior" where they would use "science" (read: an excel spreadsheet) to determine which of two kinds of historical soldier was best? It was fake AF but it was super fun to watch. I loved the little fights they put at the end of each episode.

Also OP, to answer your question, it depends on the circumstances. 1v1 it's probably the samurai since they lived into the early industrial age and therefore had access to way better armour and weapons (and also nutrition) than the bronze age Spartans. But if it's a 30v30 formation battle, the Spartans probably take it because spear and shield tactics are OP as heck.

Who would win in a fight? A half-naked militiaman with a bronze sword or a soldier in full armor with a steel katana?

Don't get me wrong, Greek hoplites were great in formation for their time period, but the individual spartan was basically just a decently fit dude

Samurai came later and were better armored / also capable of dueling whereas hoplites were squad fighters and had, at best, iron armaments.

Are we talking 1 on 1? I'm no expert, but didn't Spartans usually fight in groups with interlinked shields? So perhaps that type of shield wouldn't help much in this situation. I guess whoever could get a jab in between the armour of their opponent faster. My money would be on the samurai, but I think it would be a close fight.

Neither, a ninja is actually hiding in the Spartan's shadow waiting to kill them both but then all three get killed by a pirate who swung down on a rope with a sword in one hand and a knife in his teeth

Spartans were way better trained as being royalty who should have been exclusively occupied with warfare in addition to their own propaganda that they were invaders and that the helots would betray them first time they could.

Practicing on live helots, being barred from politics until you were old enough and the puritanism all played into making them the most formidable.

I think that despite spartan losses, they almost always had the edge in the training and morale for the average citizen.

Sparta feels like if the Navy seals lead a state. The Shogunate feels more like a long lived junta with feudalism.

One is probably better at individual combat whereas the other at formation combat so...