It does last long. Look at Jiraiya vs Pain. All you need is someone to regenerate the chakra for you (the toads) or in naruto's case, clones.I say MS! Because you get the amaterasu, tsukuyomi and susanoo...and for sage mode, it just strengthens your attacks...and it doesn't really last that long. Correct me if I'm wrong. Now I'm just wondering what will Sasuke look like if he has sage mode at the same time with mangekyo sharingan.