Ok. I watched the video. I still disagree with that, and I don't think it's arbitrary to prefer SSA to SIA. I think that follows necessarily from the consideration that you could not have noticed yourself not existing.

In any case, whatever you say about probability, being surprised is something that happens in real life. And if someone did the Sleeping Beauty experiment on me in real life, but so that the difference was between 1/100,000 and 1/2, and then asked me if I thought the coin was heads or tails, I would say I didn't know. And then if they told me it was heads, I would not be surprised. That shows that I agree with the halfer reasoning and disagree with the thirder reasoning.

Whether or not it makes sense to put numbers on it, either you're going to be surprised at the result or not. And I would apply that to basically every case of SSA argument, including the Doomsday argument; I would be very surprised if 1,000,000 years from now humanity has spread all over the universe.