However, as the person who actually runs the relevant promo committees for the org, both would be fine, i'd care a lot more about why the choice was made.
> Googlers have the experience but not the distance to meaningfully comment on google.
Yes, having experience is still better than outright making things up because you have neither the experience, nor data or any kind of basis for a claim.
Option 1 will take a long time. Writing a libc takes a long time, and transitioning the whole of Google codebase to a new libc takes even longer to iron out all of the incompatibilities.
If one goes with option 2, he/she may have many more achievements to write on his/her promotion packet during the time he/she would have spent implementing a new libc. So I hardly think promotion is the incentive here.
However, as the person who actually runs the relevant promo committees for the org, both would be fine, i'd care a lot more about why the choice was made.