Hi, Christian,

I would always suggest installing the add-ons locally/on test server first, since any package/add-on might break the site. Having said that, leaving this decision for administrators might be dangerous, since they might try to install the add-on directly on production without testing. 

Therefore, I would always advice using Code option, since you have better control over testing/releases. 

Apart from that, when you are installing from code, you have control over what is installed and can't go into "which-environment-has-what-installed" dillemas. You don't need to install after deploying to the next environment, etc.

BR,

Marija