As the victim of the larger pre-Shai-Hulud attack, unfortunately the install script validation wouldn't have protected you. Also, if you already have an infected package on the whitelist, a new infection in the install script will still affect you.

I’m not sure why but bun still feels snappier.

This is why: https://bun.com/blog/behind-the-scenes-of-bun-install

Aside from speed, what would the major selling points be on migrating from pnpm to bun?

Are there any popular packages that require postinstall scripts that this hurts?

A whitelist in package.json is only a partial assist