meaning of "what wouldn't I say?"

[morningtrain]

M: Where's your hometown?
W: I come from a small town outside of Seoul.
M: Oh. Well, if you were to compare that town to Seoul, what would you say?
W: What wouldn't I say? It's completely different!

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What does "what wouldn't I say?" mean here? Does that mean "I have no idea."? If not, "I have nothing to say?"

Could you tell me when you usually use this expression? Any comments would be appreciated.

[Rover_KE]

What does "what wouldn't I say?" mean here? Does that mean "I have no idea."? If not, "I have nothing to say?"

It means the exact opposite: 'I have such a lot to say (that I hardly know where to start).'

You could also say 'How long have you got? (It will take me such a long time to answer your question.)'

Rover

[morningtrain]

Thanks for your explanation, Rover_KE. So helpful.