Possible consideration: meta-charities like GWWC and 80k cause donations to causes that one might not think are particularly important. E.g. I think x-risk research is the highest value intervention, but most of the money moved by GWWC and 80k goes to global poverty or animal welfare interventions. So if the proportion of money moved to causes I cared about was small enough, or the meta-charity didn't multiply my money much anyway, then I should give directly (or start a new meta-charity in the area I care about).

A bigger possible problem would be if I took considerations like the poor meat eater problem to be true. In that case, donating to e.g. 80k would cause a lot of harm even though it would move a lot of money to animal welfare charities, because it causes so much to go to poverty relief, which I could think was a bad thing. It seems like there are probably a few other situations like this around.

Do you have figures on what the return to donation (or volunteer time) is for 80,000 hours? i.e. is it similar to GWWC's $138 of donations per $1 of time invested? It would be helpful to know so I could calculate how much I would expect to go to the various causes.