While true, I doubt the first effect would be significant. You're not very likely to be the one responsible for saving the earth and, singularity aside, terrestrial effects are likely to be far more important to you.

Contrawise, if you were capable of running a simulation, the odds of your input being relevant for existential are much higher. You might be running the simulation to help other people decide whether or not to be religious, or whether to persuade others to be religious, but then it becomes a lot more likely that the combined reduction in epistemic rationality would become an existential issue.