I'd probably actually diversify since it seems like a positive sum game between the egoist in me and the altruist in me. The egoist more wants actual, real status/reward, which tends to only be gained when you pick an actual winner. People don't give you any praise for anything other than actual, real successes, I find. And if the expected marginal utilities of the top 5 causes are comparable (the same to within a factor of 2), the altruist isn't actually conceding very much.