It's hard to say. He has techniques that only use one sword, but I also recall him struggling in instances where he didn't have his full array of swords. I don't think each sword is equal, as in losing each sword accounts for a 33% loss in power/skill. It's probably more like this:
3 swords: 100
2 swords: 80
1 sword: 50
Progressively gets worse with the loss of each sword.