The top considerations that come into play when I advise someone whether to earn-to-give or work directly on x-risk look like this:

1) Does this person have a large comparative advantage at the direct problem domain? Top-rank math talent can probably do better at MIRI than at a hedge fund, since there are many mathematical talents competing to go into hedge funds and no guarantee of a good job, and the talent we need for inventing new basic math does not translate directly into writing the best QT machine learning programs the fastest.

2) Is this person going to be able to stay motivated if they go off on their own to earn-to-give, without staying plugged into the community? Alternatively, if the person's possible advantage is at a task that requires a lot of self-direction, will they be able to stay on track without requiring constant labor to keep them on track, since that kind of independent job is much harder to stick at then a 9-to-5 office job with supervision and feedback and cash bonuses?

Every full-time employee at a nonprofit requires at least 10 unusually generous donors or 1 exceptionally generous donor to pay their salary. For any particular person wondering how they should help this implies a strong prior bias toward earning-to-give. There are others competing to have the best advantage for the nonprofit's exact task, and also there are thousands of job opportunities out there that are competing to be the maximally-earning use of your exact talents - best-fits to direct-task-labor vs. earning-to-give should logically be rare, and they are.

The next-largest issue is motivation, and here again there are two sides to the story. The law student who goes in wanting to be an environmentalist (sigh) and comes out of law school accepting the internship with the highest-paying firm is a common anecdote, though now that I come to write it down, I don't particularly know of any gathered data. Earning to give can impose improbability in the form of likelihood that the person will actually give. Conversely, a lot of the most important work at the most efficient altruistic organizations is work that requires self-direction, which is also demanding of motivation.

I should pause here to remark that if you constrain yourself to 'straightforward' altruistic efforts in which the work done is clearly understandable and repeatable and everyone agrees on how wonderful it is, you will of course be constraining yourself very far away from the most efficient altruism - just like a grant committee that only wants to fund scientific research with a 100% chance of paying off in publications and prestige, or a VC that only wanted to fund companies that were certain to be defensible-appearing decisions, or someone who constrained their investments to assets that had almost no risk of going down. You will end up doing things that are nearly certain never to appear to future historians as a decisive factor in the history of Earth-originating intelligent life; this requires tolerance for not just risk but scary ambiguity. But if you want to work on things that might actually be decisive, you will end up in mostly uncharted territory doing highly self-directed work, and many people cannot do this. Just as many other people cannot sustain altruism without being surrounded by other altruists, but this can possibly be purchased elsewhere via living on the West or East Coast and hanging around with others who are earning-to-give or working directly.

These are the top considerations when someone asks me whether they should work directly or earn to support others working directly - the low prior, whether the exact fit of talent is great enough to overcome that prior, and whether the person can sustain motivation / self-direct.