Eh, afaik /usr/local was for storing stuff installed by the local sysadmin and not distributed by the vendor… ~/.local the was for stuff compiled by each individual user and installed locally (in their home directory).

The idea is that if a user needs some kind of software and is able to build it autonomously then they can set $PATH and other environment variables to make it available to the session. Please note that in ~/.local there are bin, man, lib and other directories, so you can pretty much build, install and run what you need without bothering your sysadmin :)

These days… some package managers might put stuff in there so that they can work without needing root permission and without messing up with the general system.