Translations:USE flag/33/en
From Gentoo Wiki
For the end user, whether a USE flag is "global" or "local" has little importance. "Global" flags may sometimes be more suited to being set in the USE variable in make.conf, but there is absolutely no hard rule. In any case, as much as possible, no USE flags should be set in make.conf unless necessary, and /etc/portage/package.use should be preferred to set USE flags on a per-package basis. Following this advice should ease system administration in the long run.