>"at scale" here means # of contributors, not # of lines or scope of code base.

I understood what you meant, I just disagree that this is a real consideration. Both are just UI frameworks following modern conventions in architecting your SPA code-base. From that point, both are just fine. Other considerations, like the fact that React is more popular and therefore more likely to be supported in the future, and therefore has more devs familiar with it, are way more important.