I don't claim it's worse; I'm not convinced it's better. Here they behave the same, and I think it's a pretty significant failure on both their parts. If I had to argue that IRV is worse than FPTP, I'd point out that voters already know what sort of strategic voting FPTP expects of them, while IRV is often sold on the premise that voters don't need to vote strategically and so is more likely to hit those failure modes in more damaging ways as we learn... but there's a degree of devil's advocate there. I do worry that it might be worse, but I do not claim that it is.

> Here they behave the same

Well yeah, in this particular instance they do. That doesn't mean they always do. For example, with the commonly-used Tennessee capital election scenario (https://en.wikipedia.org/wiki/Instant-runoff_voting#Tennesse...), IRV would select Knoxville while FPTP would select Memphis - still not quite optimal for everyone (Nashville would probably be the ideal winner in a "perfect" electoral system), but good enough for the majority and a strict improvement over FPTP.

Of course they don't always; certainly IRV is sometimes mechanically better. I believe we can construct examples where FPTP would happen to work out better given the same honest votes, although I do think they're more contrived - see below for details. I am more worried about what happens in practice, though; as I said, people understand with FPTP that they need to vote strategically and understand how to do that.

Contrived scenario for FPTP picking the Condorcet winner while IRV fails to:

Back to the "which theocracy, or do we just tolerance?" question, but now each religion has at least two candidates and secular tolerance has a bigger constituency.

    19% S, ...
    16% A1, A2, S, ...
    15% A2, A1, S, ...
    14% B1, B2, S, ...
    13% B2, B1, S, ...
    12% C1, C2, S, ...
    11% C2, C1, S, ...

FPTP picks S, sort of by chance, which is also the Condorcet winner. IRV consolidates the C votes behind C1, then the B votes behind B1, then the A votes behind A1, then discards S.

I think that works out, FPTP makes the right choice for sort of the wrong reason while IRV makes the wrong choice. But I do think the much bigger concern is FPTP-with-strategic-voting behaving better (or at least no worse) than IRV-with-whatever-happens-in-practice.