Originally Posted by
Shiki-pon
Not to sound too harsh, but as has been stated before, they're all kinda terrible in their own way.
Still, I'd say the best is "Gladios", not just in comparison but overall. Stats are reasonable, Skills actually have something to do with the myth, and the gladiators don't have laser cannons or some such nonsense. Your only misstep with the sheet was in the Noble Phantasm department, where you decided to give them the ability to summon Spartacus and other famous gladiators and then gave them all Tsubame Gaeshi (kinda loses the uniqueness if some random literally no-name gladiator can pull it off - then again, that description also fits Kojiro to some extent).
Still, you might want to aim for something more like that one in the future. Just tone down the Noble Phantasms and everything will be fine. It's ok for Servants to be specialized (as opposed to mastering literally everything you can think of).
Anyways, apologies for the apparent harshness (at least I answered).