I disagree, with the package manager you know that it's been vetted by the distribution maintainer, they ensure that when you install something through the package manager the package comes from them and they ensure the binaries do not change. The package maintainers will also remove packages that have major security issues and the package manager will track the apps installed and automatically update them if there's a security fix.

Curl | Bash usually runs in user context (although I've seen curl | sudo bash in the wild) but there's also concerns of vetting who wrote the instructions, if they actually point to the app or a modified version of the app containing malwares, etc...