Both when they first get their swords.
InuYasha should be able to win. He's stronger than Ichigo at this point, and not sure on Ichigo's speed when he first started. InuYasha's durability is still better than Ichigo's
what about when ichigo first gets his shikai. speed equal. no powers
Then Ichigo should win due to him having better fire power.
If Ichigo gets Getsuga InuYasha gets Windscar and/or backlash wave. Tetsuiga is still in its base form when its capable of performing these attacks anyway.
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