又 and 再 are indeed very similar, but with one small distinction: 又 is used for "actual" repetition while 再 is used for "projected" repetition. You'll most likely see 又 in the past or present tense, and 再 in the future tense if the action is considered part of a predetermined course of action.
又說又說 再說 said again; (past/ present tense) to talk/discuss again ( in the future )
又來又來 再來 come again (past/ present tense) also more disapprovingly come again; ( future tense ) also more welcome
又見又見 再見 see again (past/ present tense) see again ( future tense )