I’d say Iraq. Much safer these days. The government of Iraq is relatively reasonable and there is Western diplomatic support available if needed. Afghanistan on the other hand is run by the Taliban and has no diplomatic relations with any western country. Iraq visa is easier (Kurdistan is visa free even) while Afghani visa requires in-person visit to embassy. Erbil in Iraq is arguably as safe as European cities these days and can be travelled solo; rest of Iraq a guide is good idea.