Licenses for new code?

While Calibre being GPL v3 (with some code vendored in from a variety of different other GPL-compatible licenses) constrains much of Arcalibre to be GPL v3 as well, there is the question of what license should be used for all new code going forward, such as the spellsnake wrapper in arcalibre!14. I lean heavily towards copyleft licenses, after seeing how much "permissive" licenses have facilitated an undermining of labor rights, but even there, is GPL v3 the right answer? Are there other copyleft licenses worth considering, or other GPL variants like AGPL v3?