The best sword is the one the victor is carrying.
From our perspective "best" is subjective as we don't do much fighting with swords anymore. We can say best military sword developed in Europe by the 1400s, or best common sword design of the year 9, but then, like knives today, we can get bogged down in intended usage parameters. Was a large saber really the ideal weapon for a jailer who would probably be needing a short weapon he could use in enclosed spaces, or was a navy cutlass the best choice for facing an armored knight? Was a long fencing sword the best choice to carry when walking down the alley? When beset upon by two robbers armed with a scimitar and a cutlass, did you want a broadsword, a rapier or a Gladius? If the fight happened in an alley, would your choice change? Is your choice the same when riding into battle against knights? What if you were a spanish soldier guarding a treasure ship from raiding pirates? Would you want a samuri sword, a rapier, or a cutlass?
Even back in the days when they were common, many never used their swords. Millions of Americans own pistols, but probably well less than 5% have been in shootouts with attackers. Skill levels varied as much as handgun skill levels today vary. A .22 or a .380 is a better choice for some pistol owners than a .44. For some the .44 is a better choice. So it went with swords. You might be very skilled with a Scottish Claymore, but that little girl down the street might slice and dice you with her Persian short sword when she could barely pick up your claymore afterwards to bring home to her brother as a gift.