I think the simplest version of that thought experiment is one where it's a one-off bet (double-or-nothing this universe, once). I guess the math supports saying yes to that, if the odds of winning are > .5, right?
My intuition for the reason to say no to the bet is that there's a qualitative difference between existing and not existing.
If I were offered a .51 chance of transforming this universe into one where The Beatles had recorded 20 more songs, vs one where we had never known 20 songs by them, I would say yes. That works for me regardless of the no. of songs. But when it gets to “twice as many songs” vs “no songs at all” (ie, The Beatles never existed for all practical purposes), something changes, and I would reject the bet.
…I think 🙂
