Good post; a lot of the benefits you list are speculative but seem plausible to me.
I also have experience in BP debating (though I've only attended a handful of competitions), and while I can't speak for other debating formats, in BP there is very little scope for awarding people points on the basis of their rhetorical style or how confidently they speak; in theory, debates are judged on the strength of arguments presented. (I know this is a point you were getting at in your post, but I think it's worth stating it explicitly.) In practice, of course, judges have various biases, but then I'm not sure the situation would be much different with the judges of anti-debates.
I begin with splitting my donations between cause areas: currently, 60% to longtermism and 40% to animal welfare. And then I decide which funds/orgs to give to from there.
This month, that is:
30% Long-term future fund
30% Longtermism Fund (Longview Philanthropy)
30% Animal Welfare Fund
5% Good Food Institute
I'm becoming more comfortable with 'diversifying' my donations; 2 months ago I was just giving to the Long-term Future Fund and the Animal Welfare Fund.
For me, I think a big reason I'm starting to diversify is that while I trust that the folks at all these orgs know how to spend money more effectively than I do, it perhaps makes sense to trust multiple teams of experts in case there's a more general failure at one of them. Hope that makes sense.