The sketch of the argument which favours panspermia.

1. There are around 10 billion potentially habitable planets in our galaxy.

2. Interstellar panspermia of small organisms will inseminate all of them with life in a few billion years.

3. Abiogenesis could be the main filter. Recent estimate of the minimum length of self-replicating RNA is around 100 bases. Totani thinks that only one of 10^100 Suns will generate correct RNA and start RNA-world. Thus only one of 10^80 of universes has life. Thus it looks like Rare Earth is true and we are alone.

4. However, there are many different universes in the multiverse and some of them may allow panspermia.

5. The density of planets with life in a pasnpermia-universe is 10 billion times more than such density in a non-panspermia universe as each life will colonise the whole galaxy.

6. We don't know the relation of non-panspermia to panspermia-universes. If it is less than 10 billion, we are more likely to be in panspermia-universe based on anthropic considerations, because each of them will have 10 billions times more attempts to create a civilization of a planet with life.

7. If we are in the panspermia universe, it means that the Great filter from the Fermi paradox is likely ahead, as major abiogenesis filter doesn't prevent many planets in our galaxy from having life. Rare Earth hypothesis is false locally.

8. It means that either there are a lot of aliens nearby or almost all civilizations self destruct. (Or there are some other earlier great filters like a higher level of asteroid impacts etc.) Not good from x-risks view point.