Even if there was some upper limit, which the more I think about it you are probably right on (The human brain and the nerve system would probably be unable to register something beyond a certain threshold), I would still imagine that limit to be far significantly higher than what Gojo experienced. Not to discredit Gojo, but it just seems like a single, destructive blow far beyond one's ability to endure would be more excruciating than million's of cuts on a level far closer to what that person can endure (even if as you said in that moment it was still a bit too much for Gojo, which is a commendable thing to survive even with regen), though comparing these types of pain can't be too simple, I suppose.
Bob isn't wrong either about the pain discussion being redundant, but I found it interesting at least. But yeah, Gojo can ignore with Supernatural Willpower as is, and Woody can stun via his lasso technique's, so I suppose it's moot.
That's 8 votes for Woody, yeah?