Both Sasuke and Madara had Kyuubi on their side at this point. It was the most logical decision to merge PS with Kyuubi instead using PS alone since obviously Kyuubi + PS > PS by itself.
Also about swords, Madara's v3 and v4 has this curved swords
Madara's PS swords :
Now Sasuke's v3 legged susanoo was actually using it's arrows as the sword
I thought everyone known that.
Sasuke's PS swords :
Also about swords, Madara's v3 and v4 has this curved swords
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Madara's PS swords :
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Now Sasuke's v3 legged susanoo was actually using it's arrows as the sword
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Sasuke's PS swords :
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