> By some logic, that would mean it is the most battle-tested and highest-stakes (and therefore most carefully-managed) choice
As someone who used to work on the inside, us-east-1 has the biggest pile of legacy workarounds for internal AWS issues, it has a variety of legacy API behaviours that don't exist in other regions, and because everyone picks it as the default, it has significantly more pressure on contested resources (i.e. things like spot instance pools).
Plus since it's the default in all the tooling, if you ever decide to go multi-region, you'll find tons of things break right away.
As someone who used to work on the inside, us-east-1 has the biggest pile of legacy workarounds for internal AWS issues, it has a variety of legacy API behaviours that don't exist in other regions, and because everyone picks it as the default, it has significantly more pressure on contested resources (i.e. things like spot instance pools).
Plus since it's the default in all the tooling, if you ever decide to go multi-region, you'll find tons of things break right away.