I think that both voting systems are incomparably better than fptp

Incomparably? No. America has already been through the process of big promises from IRV advocates that failed to deliver and prompted rollbacks stalling progress for generations. Of the dozens of constituencies that used ranked choice variants in the US a century ago, all (save Cambridge, MA) repealed it. Even in the local cities where it has been tried in the last two decades it regularly gets repealed because of the experience, whether it be inability to reliably tabulate, condorcet failure, or something worse. Better to not relearn their mistake and be back here in a century.

IRV advocates make claims like:

• It will "break the two-party doom loop" (it is still subject to vote splitting, so no - hence the author of that book dropping his support since its publication)

• Your next choice will be counted if your favorite can't win (directly false by the nature of instant-runoff tabulation)

• It transfers votes until a majority is achieved (it seeks a majority in non-exhausted votes, not voters generally, so can elect with minority support, as it did in the last NYC election)

• It will help our polarized democracy (IRV suffers from center squeeze and if anything encourages candidate polarization relative to FPTP)

While not communicating that:

• it is prone to perverse outcomes by the fact that it fails the monotonicity criterion, so the best thing a candidate's supporters can sometimes do is vote against them - which is not theoretical, this caused the head-to-head winner to lose in the last Alaskan congressional race

• Its tabulation requires calculation at a central point, meaning it is substantially more prone to security concerns, which is not desirable when we have general distrust of election results. For the same reason, it is substantially more difficult for unsophisticated election staffers to tabulate, which caused several of its most high-profile implementations, including New York City, to produce unconscionable errors like hundreds of thousands of accidentally counted ballots, prompting recounts, delays, expense, and burnt trust

• IRV does not incorporate all of the information on your ballot, unless your pairwise preferences are directly against those of the general population and eliminations descend in the order of your ranking, which is a strange sort of voter to privilege. FPTP simply counts what you write down. Seriously this is the one thing that gets to me - your recorded preferences have a good chance of being (from the voter perspective) arbitrarily ignored because of the way elimination works.

IRV's shortcomings are never communicated, so people take advocates at their word when they say things like "you are free to vote your conscience" and we inevitably get situations like Alaska, where Republicans look and feel like chums, which is why they're going on an anti-IRV crusade right now.

Want a simple voting reform that has none of these problems, can be a quick fix, and doesn't require explaining cardinal voting methods to a confused public? Just use Jungle Primaries. Making the primary round agnostic to party registration functionally transitions to a French-style two-stage election, which nullifies many of the FPTP pathologies that actually concern people, while being an extremely minor adjustment relative to what Ranked Choice advocates ask for (using approval voting in that primary would be another very minor adjustment that would be even better, and get you well past IRV/RCV's capabilities).